Mayflies of the Fiji Islands (Ephemeroptera)

205 Mayflies of the Fiji Islands (Ephemeroptera) Thomas Kaltenbach1,2 1 Muséum cantonal des Sciences Naturelles, Département de zoologie, Palais de Rumine, Place Riponne 6, CH-1005 Lausanne, Switzerland 2 University of Lausanne (UNIL), Department of Ecology and Evolution, CH-1015 Lausanne, Switzerland Corresponding author: Thomas Kaltenbach ([email protected]) Copyright: © Thomas Kaltenbach. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Material collected in 2024 in nine different rivers on the two main islands of Fiji, Viti Levu and Vanua Levu, is the basis for this taxonomic study of mayflies of the Fiji Islands. Apart from one larva of Caenidae, not treated in this study, all other larvae and three female imagos belong to two genera of the family Baetidae (Baetis Leach and Papuanatula Lugo-Ortiz & McCafferty). A new subgenus of Papuanatula, Fijifiliola subgen. nov., based on the larvae of ten new species, and the larva and female imago of one new species of Baetis are described and illustrated. DNA barcodes (COI) were obtained for most species, and their genetic distances were analysed (Kimura-2 parameter). A key to all species of Papuanatula (Fijifiliola) subgen. nov. is provided. Amongst the new species of Papuanatula (Fijifiliola) subgen. nov., a case of parthenogenesis and likely ovoviviparity is discussed. Key words: Baetis, COI, Fijifiliola, integrative taxonomy, ovoviviparity, Papuanatula, parthenogenesis Introduction The Fijian archipelago in the southwestern Pacific consists of more than 300 islands with a tropical, maritime climate, laying in the middle of other archipelagos, namely Vanuatu, New Caledonia, Tonga, and Samoa. It has four major islands, Viti Levu, Vanua Levu, Taveuni, and Kadavu. In terms of geology, Fiji is dominated by volcanic rocks and their erosion products (Colley 2009). Fauna and Flora of the Fiji Islands are strongly connected to New Guinea. Fiji is close enough to other island groups for dispersal to occur, likely along the Melanesian arc, which had even more islands in the past and therefore, enabled shorter dispersal distances (Flowers 1990; Ryan 2009). Later, some of the western islands of the Melanesian arc converged to become part of what is today New Guinea. This likely dispersal together with a wide range of habitats has led to a considerable diversity in the Fiji Islands (Ryan 2009). The mayfly fauna of the Fiji Islands is poorly studied. As explained in Flowers (1990), McLean (1974) published a study guide to aquatic insects of the Fiji Islands, intended for students, without formal taxonomic treatment. He listed the mayfly genera Baetis, Pseudocloeon, and Isca (Leptophlebiidae). According to Flowers (1990), Baetis refers to species of the former group molawinensis (acAcademic editor: Ben Price Received: 12 August 2025 Accepted: 29 September 2025 Published: 11 November 2025 ZooBank: https://zoobank. org/48F9008F-BC5F-49BA-994A2142AF2EAE55 Citation: Kaltenbach T (2025) Mayflies of the Fiji Islands (Ephemeroptera). ZooKeys 1259: 205–276. https://doi. org/10.3897/zookeys.1259.168521 ZooKeys 1259: 205–276 (2025) DOI: 10.3897/zookeys.1259.168521 206 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands cording to Müller-Liebenau and Hubbard 1985), which later became Labiobaetis Novikova & Kluge, 1987; Pseudocloeon refers to New Genus “A”, which is described in this study as Papuanatula (Fijifiliola) subgen. nov.; and Isca, which was based on adults only, refers to a species of Caenidae. The study of Flowers (1990) on Ephemeroptera of the Fiji Islands gives an important first view on the diversity, morphology, and biogeography of mayflies on this archipelago, but without any formal taxonomic treatment. His study was mainly based on very rich material coming from Dr. McLean’s collections in Fiji and from the University of the South Pacific’s Institute of Natural Resources Fijian aquatic insect survey in 1980. Sixty locations on four different islands (Viti Levu, Vanua Levu, Ovalau, and Ono-i-Kadavu) were covered, but most specimens came from the two largest islands, Viti Levu and Vanua Levu. Flowers (1990) reported one species of Caenidae, and 14 species of Baetidae from three genera: Baetis group molawinensis (according to Müller-Liebenau and Hubbard 1985, now Labiobaetis) with three species; New Genus “A” described herein as Papuanatula (Fijifiliola) subgen. nov. with eight species; and New Genus “B” (probably undescribed new genus; no material available for this study) with three species. He also provided figures of main characters of the different genera. Additionally, some ecological studies on streams were done on the main island Viti Levu by Haynes (1987, 1994, 1999). Haynes (1999) mentioned three species of Ephemeroptera: Cloeon sp. A, Cloeon sp. B, and Pseudocloeon sp., the latter as living on stones and boulders. Pseudocloeon certainly refers to Papuanatula, but it remains unclear to what Cloeon refers. Neither McLean (1974) nor Flowers (1990) mentioned Cloeon for the Fiji Islands, but this does not exclude their presence. Cloeon has a worldwide distribution, some species are successful colonisers, and its presence on Vanuatu has been confirmed (Gattolliat and Staniczek 2011). The Bishop Museum of Hawaii provided a checklist of Ephemeroptera of Fiji compiled by Evenhuis (2007), in which all the above-mentioned species are listed. Currently, the genus Papuanatula Lugo-Ortiz & McCafferty, 1999 (Baetidae) comprises 33 species, 32 endemic to New Guinea including the island of New Britain, and one species from Sulawesi (Lugo-Ortiz and McCafferty 1999; Kaltenbach et al. 2025a, b). In this study, ten new species of Papuanatula are described and illustrated based on larvae, all belonging to the new subgenus Fijifiliola subgen. nov., which is also described. The material was collected by the author in 2024 in nine rivers on Viti Levu and Vanua Levu (Table 2). Considering the high diversity of Papuanatula in the Fiji Islands and the limited locations investigated so far, we must expect further new species in the future, also when the historical material from this archipelago is studied in more detail. Surprisingly, a new species of Baetis was also discovered, far from the closest known occurrences of the genus in Southeast Asia, Taiwan, or Japan; currently, the genus is not known from New Guinea. Larvae and female imagos of the new species are described and illustrated. Collections in surrounding archipelagos, especially toward New Guinea, may show if it is an isolated population in the Fiji Islands, or somehow connected to other records of the genus. Materials and methods The larvae and three female imagos were collected by kick-sampling and preserved in 96% ethanol. Dissection of larvae and imagos was done in Cellosolve 207 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands (2-Ethoxyethanol) with subsequent mounting on slides with Euparal liquid, using an Olympus SZX7 stereomicroscope. The DNA of part of the specimens was extracted using non-destructive methods allowing subsequent morphological analysis (see Vuataz et al. 2011 for details). We amplified a 658 bp fragment of the mitochondrial gene cytochrome oxidase subunit 1 (COI) using the primers LCO 1490 and HCO 2198 (Folmer et al. 1994). Sequencing was done with Sanger’s method (Sanger et al. 1977). Genetic variability between specimens was estimated using Kimura-2-parameter distances (K2P, Kimura 1980), calculated with the program MEGA 11 (Tamura et al. 2021, http://www.megasoftware.net). The GenBank accession numbers are given in Table 1; nomenclature of gene sequences follows Chakrabarty et al. (2013). Photographs of larvae in toto were taken using a Canon EOS 6D camera and processed with the programs Adobe Photoshop Lightroom (http://www.adobe. com) and Helicon Focus v. 5.3 (http://www.heliconsoft.com). Photographs of larval and imaginal parts were taken with an Olympus SC 50 camera on an Olympus BX43 microscope, processed with the program Olympus Cell Sense v. 3.2. Photographs were subsequently enhanced with Adobe Photoshop Elements 13. Distribution maps were generated with the program SimpleMappr (https:// simplemappr.net, Shorthouse 2010). Coordinates and description of sample locations are given in Table 2. The dichotomous key was elaborated with support of the program DKey v. 1.3.0 (http://drawwing.org/dkey, Tofilski 2018). The terminology follows Kluge (2004). The term “blank” is used to describe an unpigmented area of cuticle (Kluge et al. 2023). The term “posterior seta/setae” is used for long setae in posterior position of the claw (approximately opposite to the distalmost denticle), as proposed by Kluge and Novikova (2014). All material has been deposited in the Muséum cantonal des Sciences Naturelles, Lausanne, Switzerland (MZL). Results Genus Baetis Leach, 1815 Baetis procul sp. nov. https://zoobank.org/0C33CE39-3BFE-4C55-8ADB-AAECDAD8135A Figs 1–4 Material examined. Holotype. FIJI • larva; Viti Levu, Ba Prov., Sabeto Riv., near Sabeto; 17°43'09"S, 177°31'21"E; 30 m; 17.xi.2024; leg. T. Kaltenbach; on slides; GBIFCH01221812, GBIFCH01221813; MZL. Paratypes. • 11 larvae; same data as holotype; 2 on slides; GBIFCH01221839, GBIFCH01581967, GBIFCH01581968; 9 in alcohol; GBIFCH01581966, GBIFCH01581969, GBIFCH01581970; MZL • 3 female imagos; Viti Levu, Ba Prov., Ba Riv., near Outback Hotel; 17°37'35"S, 177°45'04"E; 20 m; 22.x.2024; leg. T. Kaltenbach; 1 on slide; GBIFCH01221835; 2 in alcohol; GBIFCH01581964, GBIFCH01581965; MZL. Diagnosis. Larva. Following combination of characters differentiate Baetis procul sp. nov. from other species of Baetis, some of the characters also from 208 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Table 1. Sequenced specimens (COI). Species Specimen voucher catalogue # Island Locality code GPS coordinates GenBank # (COI) GenSeq nomenclature P. (F.) aji sp. nov. GBIFCH00975846 Viti Levu A 17°37'35"S, 177°45'04"E PX067251 genseq-2 COI GBIFCH00975847 Viti Levu A 17°37'35"S, 177°45'04"E PX067252 genseq-2 COI GBIFCH01581961 Viti Levu B 17°37'33"S, 177°45'15"E PX067253 genseq-2 COI GBIFCH01581939 Viti Levu C 17°40'26"S, 177°33'06"E PX067254 genseq-2 COI GBIFCH01581953 Viti Levu C1 17°40'07"S, 177°32'31"E PX067255 genseq-2 COI GBIFCH01581925 Viti Levu C1 17°40'07"S, 177°32'31"E PX067256 genseq-2 COI GBIFCH01582018 Viti Levu C1 17°40'07"S, 177°32'31"E PX067257 genseq-2 COI GBIFCH01582021 Viti Levu C1 17°40'07"S, 177°32'31"E PX067258 genseq-2 COI GBIFCH01582022 Viti Levu C1 17°40'07"S, 177°32'31"E PX067259 genseq-2 COI GBIFCH01582024 Viti Levu C1 17°40'07"S, 177°32'31"E PX067260 genseq-2 COI GBIFCH01581917 Viti Levu D 17°38'12"S, 177°45'29"E PX067262 genseq-2 COI GBIFCH01581918 Viti Levu D 17°38'12"S, 177°45'29"E PX067263 genseq-2 COI GBIFCH01581976 Viti Levu I 17°43'09"S, 177°31'21"E PX067270 genseq-2 COI GBIFCH01581977 Viti Levu I 17°43'09"S, 177°31'21"E PX067268 genseq-2 COI GBIFCH01581978 Viti Levu I 17°43'09"S, 177°31'21"E PX067269 genseq-2 COI GBIFCH01582028 Viti Levu I 17°43'09"S, 177°31'21"E PX067261 genseq-2 COI GBIFCH01581954 Vanua Levu E 16°39'55"S, 179°20'03"E PX067264 genseq-2 COI GBIFCH01581909 Vanua Levu E1 16°39'54"S, 179°20'01"E PX067265 genseq-2 COI GBIFCH01581987 Vanua Levu F 16°36'25"S, 179°08'46"E PX067267 genseq-2 COI GBIFCH01581986 Vanua Levu F 16°36'25"S, 179°08'46"E PX067266 genseq-2 COI P. (F.) claudia sp. nov. GBIFCH01581930 Viti Levu C 17°40'26"S, 177°33'06"E PX067280 genseq-2 COI GBIFCH01581934 Viti Levu C 17°40'26"S, 177°33'06"E PX067279 genseq-2 COI P. (F.) crussetae sp. nov. GBIFCH01582032 Viti Levu C 17°40'26"S, 177°33'06"E PX067281 genseq-1 COI P. (F.) sekawa sp. nov. GBIFCH01581904 Vanua Levu E 16°39'55"S, 179°20'03"E PX067294 genseq-2 COI GBIFCH01581903 Vanua Levu E 16°39'55"S, 179°20'03"E PX067293 genseq-2 COI GBIFCH01581908 Vanua Levu E 16°39'55"S, 179°20'03"E PX067292 genseq-2 COI P. (F.) gattolliati sp. nov. GBIFCH01581907 Vanua Levu E 16°39'55"S, 179°20'03"E PX067284 genseq-2 COI GBIFCH01581989 Vanua Levu F 16°36'25"S, 179°08'46"E PX067285 genseq-2 COI P. (F.) grisea sp. nov. GBIFCH01581940 Viti Levu A 17°37'35"S, 177°45'04"E PX067286 genseq-2 COI GBIFCH01582011 Viti Levu A 17°37'35"S, 177°45'04"E PX067288 genseq-2 COI GBIFCH01582029 Viti Levu A 17°37'35"S, 177°45'04"E PX067287 genseq-2 COI GBIFCH01581958 Viti Levu B 17°37'33"S, 177°45'15"E PX067289 genseq-2 COI GBIFCH01582026 Viti Levu I 17°43'09"S, 177°31'21"E PX067291 genseq-2 COI GBIFCH01581972 Viti Levu I 17°43'09"S, 177°31'21"E PX067290 genseq-2 COI P. (F.) flowersi sp. nov. GBIFCH01581952 Viti Levu C1 17°40'07"S, 177°32'31"E PX067283 genseq-2 COI GBIFCH01581932 Viti Levu C 17°40'26"S, 177°33'06"E PX067282 genseq-2 COI P. (F.) bula sp. nov. GBIFCH01581915 Viti Levu D1 17°38'22"S, 177°45'30"E PX067271 genseq-2 COI GBIFCH01581981 Viti Levu G 18°10'57"S, 177°44'13"E PX067272 genseq-2 COI GBIFCH01581982 Viti Levu G 18°10'57"S, 177°44'13"E PX067273 genseq-2 COI GBIFCH01581980 Viti Levu G 18°10'57"S, 177°44'13"E PX067274 genseq-2 COI GBIFCH01582014 Viti Levu G 18°10'57"S, 177°44'13"E PX067275 genseq-2 COI GBIFCH01581920 Viti Levu H 18°03'35"S, 178°28'11"E PX067276 genseq-2 COI GBIFCH01581956 Viti Levu H 18°03'35"S, 178°28'11"E PX067278 genseq-2 COI GBIFCH01581955 Viti Levu H 18°03'35"S, 178°28'11"E PX067277 genseq-2 COI B. procul sp. nov. GBIFCH01581965 Viti Levu B 17°37'33"S, 177°45'15"E PX067250 genseq-2 COI GBIFCH01581967 Viti Levu I 17°43'09"S, 177°31'21"E PX067247 genseq-2 COI GBIFCH01581968 Viti Levu I 17°43'09"S, 177°31'21"E PX067248 genseq-2 COI GBIFCH01581969 Viti Levu I 17°43'09"S, 177°31'21"E PX067249 genseq-2 COI 209 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Table 2. Sample locations (Figs 36–38; w: width, d: depth). Location code Island GPS coordinates Altitude River Characteristics (surroundings/size/ velocity/riv. bed) AViti Levu 17°37'35"S, 177°45'04"E 20 m Ba River farmland, secondary forest w: 20 m; d: 0.1–0.3 m medium fast mainly cobble B Viti Levu 17°37'33"S, 177°45'15"E 20 m Ba River farmland, secondary forest w: 20 m; d: 0.1–0.3 m medium fast mainly cobble C Viti Levu 17°40'26"S, 177°33'06"E 690 m Savuione River primary rainforest, pristine narrow river, close to waterfall very fast, turbulent bedrock C1 Viti Levu 17°40'07"S, 177°32'31"E 510 m Savuione River secondary rainforest, pristine narrow, shallow runs on rock surface fast, turbulent bedrock DViti Levu 17°38'12"S, 177°45'29"E 160 m tributary of Ba River farmland, open grassland, disturbed w: 0.5–1 m; d: 0.1–0.2 m slow muddy, algae, stones, cobble D1 Viti Levu 17°38'22"S, 177°45'30"E 220 m tributary of Ba River farmland, open grassland, disturbed w: 0.5–1 m; d: 0.1–0.2 m slow muddy, algae, stones, cobble EVanua Levu 16°39'55"S, 179°20'03"E 30 m tributary of Sekawa River rainforest, pristine w: 5 m; d: 0.2 m medium fast mainly cobble E1 Vanua Levu 16°39'54"S, 179°20'01"E 30 m Sekawa River forest, open grassland, disturbed w: 10 m; d: 0.2 m medium fast cobble, sand, filamentous algae cover FVanua Levu 16°36'25"S, 179°08'46"E 80 m Seaqaqa River open forest, disturbed w: 5 m; d: 0.1–0.2 m medium fast cobble, gravel GViti Levu 18°10'57"S, 177°44'13"E 70 m Biausevu River rainforest, closed canopy; pristine w: 3 m; d: 0.1–0.2 m medium fast stones, sandy patches HViti Levu 18°03'35"S, 178°28'11"E 160 m Waisila Creek prim. rainforest, closed canopy; pristine w: 3–5 m; d: 0.1–0.5 m fast stones, cobble, sand IViti Levu 17°43'09"S, 177°31'21"E 30 m Sabeto River farmland, open forest, wide banks w: 10 m; d: 0.1–0.4 m medium fast stones, cobble, gravel 210 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 1. Baetis procul sp. nov., larva, habitus. a. Male, dorsal view; b. Male, lateral view; c. Female, dorsal view; d. Female, ventral view. Scale bars: 1 mm. 211 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands the most similar species Baetis taiwanensis Müller-Liebenau, 1985: tergalii present on abdominal segments I–VII; hind protopteron developed; abdominal terga I–VIII grey-brown, with distinct sublateral pale areas; femur with yellowish to yellow-brown, subapical spot on anterior side. Description. Larva (Figs 1–3). Body length 3.1–4.0 mm. Cerci ~½ body length; paracercus ~⅓ of body length. Antenna: ~ 2× head length. Colouration (Figs 1a–d, 3a, i). Head and thorax dorsally grey with indistinct yellowish grey pattern as in Fig. 1a, c. Abdominal terga I–VIII dorsally greybrown, with distinct sublateral, yellowish grey markings; terga IX and X yellowish grey. Fore protoptera grey. Thorax and abdomen ventrally pale yellowish grey, laterally with grey streaks. Legs off-white, femur distomedially with grey marking, tibia and tarsus distally darker. Caudalii off-white, with dark brown section in middle part, cerci with additional dark brown section subdistally. Labrum (Fig. 2a, b). Sub-rectangular, length 0.6× maximum width. Distal margin with medial emargination and small process. Dorsally with pair of submedian setae, and submarginal arc of three or four medium to long, simple setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid, feathered setae. Right mandible (Fig. 2f). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, smooth. Tuft of setae on proximal corner of mola present. Left mandible (Fig. 2e). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola almost straight, with few minute denticles. Tuft of setae on proximal corner of mola absent. Both mandibles with lateral margins almost straight. Hypopharynx and superlinguae (Fig. 2d). Lingua approx. as long as superlinguae. Lingua longer than broad; medial tuft of stout setae poorly developed, short. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin. Maxilla (Fig. 2g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and three short to long, simple setae. Maxillary palp slightly longer than length of galea-lacinia; 2-segmented; palp segment II ~1.1× as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of segment II slightly pointed. Labium (Fig. 2c). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~7 spine-like seta; apex with three long robust setae; outer margin with ~3 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and two short, simple setae in anteromedial area; dorsally with four long, spinelike setae near inner margin. Labial palp with segment I approx. as long as length of segments II and III combined. Segment II without developed distomedial protuberance; dorsally with two or three spine-like setae near outer margin. Segment III nearly semicircular; length ~0.8× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae. Hind protoptera (Fig. 2i) present, well developed. 212 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 2. Baetis procul sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Head; i. Hind protopteron (arrows: costal margin). Scale bars: 100 µm (h); 20 µm (a, c–g); 10 µm (b, i). 213 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 3. Baetis procul sp. nov., larva. a. Hind leg; b. Femur, outer margin; c. Femur, inner margin; d. Tibia; e. Tarsus, claw; f. Femoral patch, fore leg; g. Femoral patch, middle leg; h. Femoral patch, hind leg; i. Abdomen; j. Abdominal segments; k, l. Tergalius IV; m. Paraproct. Scale bars: 100 µm (i); 50 µm (a); 20 µm (k); 10 µm (b–h, j, l, m). 220 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands MZL • 13 larvae; Vanua Levu, Cacaudrove Prov., tributary to Sekawa Riv., near Nakawaga; 16°39'55"S, 179°20'03"E; 32 m; 29.x.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581954, GBIFCH01582016, GBIFCH01582017; MZL • 4 larvae; Vanua Levu, Cacaudrove Prov., Sekawa Riv., many filamentous algae; near Nakawaga; 16°39'54"S, 179°20'01"E; 32 m; 29.x.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581909, GBIFCH01581910; MZL • 14 larvae; Vanua Levu, Cacaudrove Prov., Seaqaqa Riv., bridge near Saivou village; 16°36'25"S, 179°08'46"E; 80 m; 05.xi.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581900, GBIFCH01581984, GBIFCH01581985, GBIFCH01581986, GBIFCH01581987; MZL • 42 larvae; Viti Levu, Ba Prov., Sabeto Riv., near Sabeto; 17°43'09"S, 177°31'21"E; 30 m; 17.xi.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581971, GBIFCH01581973, GBIFCH01581974, GBIFCH01581975, GBIFCH01581976, GBIFCH01581977, GBIFCH01581978, GBIFCH01582027, GBIFCH01582028; MZL • 1 larva; Viti Levu, Ba Prov., near Abaca village, Savuione Riv., close below Savuione waterfall; 17°40'26"S, 177°33'06"E; 690 m; 24.x.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581939; MZL • 16 larvae; Viti Levu, Ba Prov., near Abaca village, Savuione Riv.; 17°40'07"S, 177°32'31"E; 510 m; 24.x.2024; leg. T. Kaltenbach; 1 on slide; GBIFCH01581928; 15 in alcohol; GBIFCH01581924, GBIFCH01581926, GBIFCH01581927, GBIFCH01582018, GBIFCH01582021, GBIFCH01582022, GBIFCH01582023, GBIFCH01582024, GBIFCH01582025; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. aji sp. nov. from other species of Fijifiliola subgen. nov.: fore protoptera posteromedially with minute spine (Fig. 7k); labrum without small process in distomedial emargination; labial palp segment III conical, pointed; abdominal tergum I grey, II, III, VII, and VIII blackish, IV–VI, IX, and X yellowish grey with blackish markings as in Fig. 6a, b; femur anteriorly with dark brown hypodermal streak in mediobasal blank (usually developed on fore femur, less on middle femur and absent on hind femur); femur anteriorly with large grey-brown marking in distomedial area, yellowish in subdistal area; paracercus with eight segments. Description. Larva (Figs 6–8). Body length 2.8–3.5 mm, cerci ~1.5× body length. Colouration (Figs 6a–c, 8f). Head and thorax dorsally dark grey with indistinct pattern, fore protoptera grey with dark grey margins. Abdominal tergum I grey, II, III, VII, and VIII blackish, IV–VI, IX, and X yellowish grey with blackish markings as in Fig. 6a, b. Thorax and abdomen ventrally grey to reddish grey, sternites VII and VIII darker. Legs grey; femur on anterior side apically, distomedially, and basally dark grey, basal area with large blank and hypodermal streak inside (developed on fore femur, poorly developed on middle femur, absent on hind femur), subdistal area yellowish; femur of all legs on posterior side with brown streak in distomedial area along outer margin. Caudalii grey. Head. Antenna (Fig. 8j). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 7a, b). Length 0.6× maximum width. Distomedial emargination without protuberance. Otherwise, as typical for subgenus. Right mandible (Fig. 7f). Margin between prostheca and mola straight, smooth. Otherwise, as typical for subgenus. Left mandible (Fig. 7e). Margin between prostheca and mola straight, smooth. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 7d). As typical for subgenus. 221 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 7. Papuanatula (Fijifiliola) aji sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Paracercus; i. Cercus; j. Male mature larva, developing subimaginal gonostylus; k. Fore protoptera, protuberance. Scale bars: 20 µm (a, c–h). 10 µm (b, i–k). 222 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 8. Papuanatula (Fijifiliola) aji sp. nov., larva. a. Hind leg; b. Femur, outer margin; c. Tibia; d. Tarsus, outer margin; e. Tarsus, claw; f. Abdomen; g. Abdominal terga; h. Paraproct; i. Tergalius IV; j. Head. Scale bars: 100 µm (f, j). 50 µm (a); 10 µm (b–e, g–i). 223 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Maxilla (Fig. 7g). Maxillary palp approx. as long as galea-lacinia; palp segment II ~1.4× longer than segment I. Otherwise, as typical for subgenus. Labium (Fig. 7c). Paraglossa with two spine-like setae on inner, distolateral margin. Labial palp with segment I subequal in length to segments II and III combined. Segment II dorsally with row of five spine-like setae near outer, distolateral margin. Segment III conical, pointed, 0.6× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 8a–e). Ratio of leg segments: fore leg 1.0:1.0:0.4:0.2, middle leg 1.1:1.0:0.4:0.2 and hind leg 1.1:1.0:0.4:0.2. Femur. Length ~3 × maximum width. Tibia. With one row of short, blunt setae parallel to row of long, fine, simple setae. Claw with one row of 11–14 denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 8f, g). Posterior margin of terga: I smooth, without denticles; II–IX with short, triangular, mostly split denticles. Tergalii (Fig. 8i). Elongate oval, rather narrow; tracheation mainly limited to main trunk; margin smooth, with short, fine, simple setae. Paraproct (Fig. 8h). Posterior margin with prolongation, with split denticles in distal part. Caudalii (Fig. 7h, i). Cerci without swimming setae. Paracercus with 7–10 segments. Pose of subimaginal gonostyli under larval cuticle (Fig. 7j). As typical for subgenus. Segment III conical. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. By far the most widespread and most frequent Papuanatula species of Fiji. Larvae usually living in run or riffles of medium fast flowing lowland rivers, sometimes in fast flowing, turbulent mountain rivers (Figs 36b–e, 37a, b, 38a–c). Occurs in more pristine rivers as well as in rivers influenced by human activities. Etymology. The species is dedicated to AJ, the owner of the Outback Hotel, where the type locality is located. He and his family provided great support during our stay and on collection excursions. Distribution. Fiji: Viti Levu, Vanua Levu (Fig. 39b). Papuanatula (Fijifiliola) aurantica sp. nov. https://zoobank.org/36040D0D-8862-4C6F-8DAF-41FB6F1B0C24 Figs 9–11 Material examined. Holotype. FIJI • larva; Viti Levu, Serua Prov., Biausevu Riv., near Biausevu; 18°10'57"S, 177°44'13"E; 70 m; 10.xi.2024; leg. T. Kaltenbach; on slides; GBIFCH01221830, GBIFCH01582013; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. aurantica sp. nov. from other species of Fijifiliola subgen. nov.: Head, thorax, and abdomen predominantly orange to orange-brown; legs in basal part with orange-brown, hypodermal marking in oval blank; medially with broad, grey band; 224 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 9. Papuanatula (Fijifiliola) aurantica sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. 225 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 10. Papuanatula (Fijifiliola) aurantica sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Head; i. Paracercus; j, k. Cerci. Scale bars: 100 µm (h); 20 µm (a, c–g, i); 10 µm (b, j, k). 226 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands with orange streak along outer margin and orange in subdistal part; labial palp segment III slightly pentagonal; paracercus with 14 segments. Description. Larva (Figs 9–11). Body length ~3 mm, cerci ~1.3× body length. Colouration (Fig. 9a–c). Head, thorax and abdomen dorsally predominantly orange to orange-brown, thorax with indistinct pattern, fore protoptera grey; abdominal terga I–III laterally with oblique, brown streaks. Head, thorax, and abdomen ventrally beige. Legs in basal part with orange-brown, hypodermal marking in oval blank; medially with broad, grey band; with orange streak along outer margin and orange in subdistal part; distally dark grey; femur of all legs on posterior side with brown streak in distomedial area along outer margin. Caudalii grey. Head. Antenna (Fig. 10h). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 10a, b). Length 0.6× maximum width. Otherwise, as typical for subgenus. Right mandible (Fig. 10f). Margin between prostheca and mola straight, with few minute denticles. Otherwise, as typical for subgenus. Left mandible (Fig. 10e). Margin between prostheca and mola straight, with few denticles toward subtriangular process. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 10d). As typical for subgenus. Maxilla (Fig. 10g). Maxillary palp approx. as long as galea-lacinia; palp segment II ~1.2× longer than segment I. Otherwise, as typical for subgenus. Labium (Fig. 10c). Paraglossa with two spine-like setae on inner, distolateral margin. Labial palp with segment I ~1.2× length of segments II and III combined. Segment II dorsally with row of four or five spine-like setae near outer, distolateral margin. Segment III slightly pentagonal, 0.7× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 11a–f). Ratio of leg segments: fore leg 0.9:1.0:0.3:0.2, middle leg 1.1:1.0:0.4:0.2 and hind leg 1.1:1.0:0.3:0.2. Femur. Length ~3 × maximum width. Setae on outer margin long, flattened, pointed. Tibia. With one row of short, blunt setae on each side of row of long, fine, simple setae. Claw with one row of ten or eleven denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 11g). Posterior margin of terga: I smooth, without denticles; II–IX with triangular denticles. Tergalii (Fig. 11h). Elongate oval; tracheation mainly limited to main trunk, brown; scattered orange pigmentation outside tracheae; margin smooth, with short, fine, simple setae. Paraproct (Fig. 11i). Posterior margin with prolongation, with denticles. Caudalii (Fig. 10i, k). Cerci without swimming setae. Paracercus with 14 segments. Pose of subimaginal gonostyli under larval cuticle. Unknown. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Local species, only known from Biausevu River. Larvae living in run of medium fast flowing rivers (Fig. 37c), in natural forest with pristine water. Etymology. The species name refers to its predominantly orange colour, aurantica meaning orange in Latin. Distribution. Fiji: Viti Levu (Fig. 39c). 227 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 11. Papuanatula (Fijifiliola) aurantica sp. nov., larva. a. Hind leg; b. Femur, outer margin; c. Femur, inner margin; d. Tibia; e. Tarsus, outer margin; f. Tarsus, claw; g. Abdominal terga; h. Tergalius III; i. Paraproct. Scale bars: 50 µm (a); 10 µm (b–i). Papuanatula (Fijifiliola) bula sp. nov. https://zoobank.org/EFE10168-E817-4880-A720-7C36A6FEF70E Figs 12–14 Material examined. Holotype. FIJI • larva; Viti Levu, Rewa Prov., Colo-I-Suva Forest Park, creek near Coloisuva; 18°03'35"S, 178°28'11"E; 160 m; 12.xi.2024; leg. T. Kaltenbach; on slide; GBIFCH01581921; MZL. Paratypes. • 5 larvae; same 228 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands data as holotype; 1 on slide; GBIFCH01581920; 4 in alcohol; GBIFCH01581919, GBIFCH01581955, GBIFCH01581965; MZL • 6 larvae; Viti Levu, Serua Prov., Biausevu Riv., near Biausevu; 18°10'57"S, 177°44'13"E; 70 m; 10.xi.2024; leg. T. Kaltenbach; 2 on slides; GBIFCH01581982, GBIFCH01221827; 4 in alcohol; GBIFCH01581979, GBIFCH01581980, GBIFCH01581981, GBIFCH01582014; MZL • 1 larva; Viti Levu, Ba Prov., creek, near Outback Hotel; 17°38'12"S, 177°45'29"E; 157 m; 25.x.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581913; MZL • 5 larvae; Viti Levu, Ba Prov., creek, near Outback Hotel; 17°38'22"S, 177°45'30"E; 220 m; 25.x.2024; leg. T. Kaltenbach; in alcohol; GBIFCH01581915, GBIFCH01581914; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. bula sp. nov. from other species of Fijifiliola subgen. nov.: femur basally with narrow dark brown to red-brown, longitudinal streak in large blank; abdominal terga II, VII, VIII dark brown, I, III–V, IX, X brighter, washy grey-brown; labial palp segment III slightly pentagonal; paracercus with 13–15 segments; cerci in middle part with one medium swimming seta each 2nd segment (Fig. 13j). Description. Larva (Figs 12–14). Body length 2.9–4.5 mm, cerci ~1.4× body length. Colouration (Figs 12a–c, 13l). Head dorsally brown, with dark brown markings; thorax dorsally dark brown; abdominal terga II, VII, VIII dark brown, I, III–V, IX, X brighter, washy grey-brown. Legs grey-brown; femur on anterior side in basal part with narrow dark brown to red-brown, hypodermal, longitudinal streak in large blank; medially with indistinct, broad, dark grey band; in distal area reddish brown; femur of all legs on posterior side reddish brown in distal ⅓, with one or two parallel, dark brown, hypodermal, longitudinal streaks. Head, thorax and abdomen ventrally grey to dark grey, sternites VI–VIII darker. Caudalii grey. Head. Antenna (Fig. 13l). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 13a, b). Length 0.6× maximum width. Otherwise, as typical for subgenus. Right mandible (Fig. 13f). Margin between prostheca and mola slightly convex, smooth. Otherwise, as typical for subgenus. Left mandible (Fig. 13e). Margin between prostheca and mola straight, with few denticles toward subtriangular process. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 13d). As typical for subgenus. Maxilla (Fig. 13g, h). Maxillary palp approx. as long as galea-lacinia; palp segment II ~1.2× longer than segment I. Otherwise, as typical for subgenus. Labium (Fig. 13c). Paraglossa with one or two spine-like setae on inner, distolateral margin. Labial palp with segment I subequal to length of segments II and III combined. Segment II dorsally with row of four or five spine-like setae near outer, distolateral margin. Segment III slightly pentagonal, 0.7× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 14a–f). Ratio of leg segments: fore leg 1.0:1.0:0.4:0.2, middle leg 1.0:1.0:0.4:0.2 and hind leg 1.1:1.0:0.4:0.2. Femur. Length ~3 × maximum width. Setae on outer margin long, flattened, pointed. Tibia. With one row of short, blunt setae on each side of row of long, fine, simple setae. Claw with one row of 11 or 12 denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 14g, h). Posterior margin of terga: I smooth, without denticles; II with rudimentary denticles in middle part, III–IX with triangular, pointed denticles. 229 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 12. Papuanatula (Fijifiliola) bula sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. Tergalii (Fig. 14i). Elongate oval; tracheation well-developed, not reaching margins, brown; margin smooth, without setae. Paraproct (Fig. 14j). Posterior margin with prolongation, with split denticles. Caudalii (Fig. 13i–k). Cerci in middle area with one swimming seta each 2nd segment, distally up to three swimming setae per segment. Paracercus with 13–15 segments. Pose of subimaginal gonostyli under larval cuticle. Unknown. 236 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Left mandible (Fig. 16e). Margin between prostheca and mola straight, with few denticles toward subtriangular process. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 16d). As typical for subgenus. Maxilla (Fig. 16g). Maxillary palp approx. as long as galea-lacinia; palp segment II ~1.2× longer than segment I. Otherwise, as typical for subgenus. Labium (Fig. 16c). Paraglossa with one spine-like seta on inner, distolateral margin. Labial palp with segment I ~0.8× length of segments II and III combined. Segment II dorsally with row of five spine-like setae near outer, distolateral margin. Segment III slightly pentagonal, 0.7× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 17a–f). Ratio of leg segments: fore leg 1.1:1.0:0.4:0.1, middle leg 1.2:1.0:0.4:0.1 and hind leg 1.2:1.0:0.3:0.1. Femur. Length ~2.7 × maximum width. Tibia. With one row of short, blunt setae parallel to row of long, fine, simple setae. Claw with one row of ten or 11 denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 17g, h). Posterior margin of terga: I smooth, without denticles; II–IX with triangular, pointed, apically partly split denticles. Tergalii (Fig. 17i, j). Elongate oval; tracheation well-developed, reaching margins, brown; margin smooth, without setae. Paraproct (Fig. 17k). Posterior margin with poorly developed prolongation, with split denticles in distal part. Caudalii (Fig. 16h, i). Cerci without swimming setae, distally with one rudimentary insertion per segment. Paracercus with 8–10 segments. Pose of subimaginal gonostyli under larval cuticle. Unknown. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Local species, larvae living in run of fast flowing, turbulent mountain rivers with pristine water (Fig. 36d). There are male and female larvae, but one last instar female larva had eggs in which the larvae are already developing, indicating facultative parthenogenesis, and probably ovoviviparity (Fig. 16k, l) (see discussion). Etymology. The species is dedicated to my wife Claudia Kaltenbach for her constant support during this collection trip. Distribution. Fiji: Viti Levu (Fig. 39e). Papuanatula (Fijifiliola) crussetae sp. nov. https://zoobank.org/036A1BF5-4D13-43D1-A3FC-3FA2C1289BF9 Figs 18–20 Material examined. Holotype. FIJI • larva; Viti Levu, Ba Prov., near Abaca village, Savuione Riv., close below Savuione waterfall; 17°40'26"S, 177°33'06"E; 690 m; 24.x.2024; leg. T. Kaltenbach; on slides; GBIFCH01581936, GBIFCH01582032; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. crussetae sp. nov. from other species of Fijifiliola subgen. nov.: femur with irregular 237 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 18. Papuanatula (Fijifiliola) crussetae sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. 238 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands row of medium to long, spine-like setae at outer margin; tibia with irregular row of medium, spine-like setae parallel to row of long, fine, simple setae; distalmost seta at inner margin of tarsus not much longer than other setae; claw with one row of 16–19 denticles; tergalii in large middle part brown; paracercus with five segments. Description. Larva (Figs 18–20). Body length 4.7 mm, cerci longer than body length. Colouration (Fig. 18a–c). Head and thorax dorsally dark grey-brown with indistinct grey pattern; abdomen dorsally dark grey-brown to reddish brown, darker in middle part and laterally, terga IX and X brighter. Legs dark grey; femur on anterior side in basal ½ with large, dark brown, hypodermal, oval marking in large blank, distomedially reddish brown. Thorax ventrally off-white, abdomen ventrally yellowish grey. Caudalii grey. Head. Antenna (Fig. 19h). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 19a, b). Length 0.7× maximum width. Otherwise, as typical for subgenus. Right mandible (Fig. 19f). Margin between prostheca and mola straight, with few minute denticles. Otherwise, as typical for subgenus. Left mandible (Fig. 19e). Margin between prostheca and mola slightly convex, with few minute denticles. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 19d). As typical for subgenus. Maxilla (Fig. 19g). Maxillary palp approx. as long as galea-lacinia; palp segment II ~1.2× longer than segment I. Otherwise, as typical for subgenus. Labium (Fig. 19c). Paraglossa with two spine-like setae on inner, distolateral margin. Labial palp with segment I subequal to length of segments II and III combined. Segment II dorsally with row of six spine-like setae near outer, distolateral margin. Segment III slightly pentagonal, 0.8× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 20a–g). Ratio of leg segments: fore leg 1.2:1.0:0.5:0.2, middle leg 1.2:1.0:0.4:0.2 and hind leg 1.2:1.0:0.5:0.2. Femur. Length ~2.2× maximum width on foreleg, other legs ~2.5×. Outer margin with irregular row of medium to long, spine-like setae. Short, pointed, spine-like setae along ventral margin. Tibia. With irregular row of short to medium, spine-like setae parallel to row of long, fine, simple setae. Tarsus. Outer margin with irregular row of short to medium, spine-like setae parallel to row of long, fine, simple setae, similar to tibia. Distalmost seta at inner margin not much longer than other setae. Claw with one row of 16–19 denticles; one or two posterior setae. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 20i, j). Posterior margin of terga: I smooth, without denticles; II–IX with triangular denticles. Tergalii (Fig. 20l, m). Wide skewed oval in shape; tracheation well-developed, reaching margins, brown; scattered brown hypodermal pigmentation in large middle part. Margin with minute denticles and medium, fine, simple setae. Paraproct (Fig. 20k). Posterior margin without prolongation, smooth, without denticles. Cercotractor without denticles. Caudalii (Fig. 19i, j). Cerci without swimming setae. Paracercus with five segments. 239 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 19. Papuanatula (Fijifiliola) crussetae sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Head; i. Paracercus; j. Cercus. Scale bars: 100 µm (h); 20 µm (a, c–g, i); 10 µm (b, j). 240 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 20. Papuanatula (Fijifiliola) crussetae sp. nov., larva. a. Middle leg; b. Femur, outer margin; c. Femur, inner margin; d. Tibia, outer margin; e. Tibia, inner margin; f. Tarsus, outer margin; g. Tarsus, inner margin; h. Claw (arrow: posterior seta); i. Abdomen; j. Abdominal terga; k. Paraproct; l, m. Tergalius VI. Scale bars: 100 µm (i); 50 µm (a, l); 10 µm (b–h, j, k, m). 241 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Pose of subimaginal gonostyli under larval cuticle. Unknown. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Local species; larvae living in run of fast flowing, turbulent mountain rivers with pristine water (Fig. 36d). Etymology. The species name is based on the Latin words crus and setae, meaning leg bristles, referring to the extraordinary setation of the legs. Distribution. Fiji: Viti Levu (Fig. 39f). Papuanatula (Fijifiliola) flowersi sp. nov. https://zoobank.org/DA210268-B574-41CC-8655-D11741506A08 Figs 21–23 Material examined. Holotype. FIJI • larva; Viti Levu, Ba Prov., near Abaca village, Savuione Riv., close below Savuione waterfall; 17°40'26"S, 177°33'06"E; 690 m; 24.x.2024; leg. T. Kaltenbach; on slide; GBIFCH01581931; MZL. Paratypes. • 1 larva; same data as holotype; on slide; GBIFCH01581932; MZL • 1 larva; Viti Levu, Ba Prov., near Abaca village, Savuione Riv.; 17°40'07"S, 177°32'31"E; 510 m; 24.x.2024; leg. T. Kaltenbach; on slide; GBIFCH01581952; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. flowersi sp. nov. from other species of Fijifiliola subgen. nov.: head orange-brown; abdomen dorsally dark brown, terga III–V partly orange-brown, X orange-brown; femur dark orange-brown; apex of hypopharynx without bifid bunch of stout setae; labial palp segment III elongate conical, inner margin straight; tergalii with orange-brown pigmentation outside tracheation; paracercus with 13 segments. Description. Larva (Figs 21–23). Body length 4.9–5.6 mm, cerci ~1.2× body length. Colouration (Fig. 21a–c). Head orange-brown; thorax dorsally dark greybrown with indistinct grey pattern, fore protoptera grey; abdomen dorsally dark brown, terga III–V partly orange-brown, X orange-brown. Legs mainly orange-brown, femur apically dark brown. Thorax and abdomen ventrally dark grey, segment X orange-brown. Caudalii orange-brown. Head. Antenna (Fig. 22h). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 22a, b). Length 0.7× maximum width. Otherwise, as typical for subgenus. Right mandible (Fig. 22f). Margin between prostheca and mola straight, smooth. Otherwise, as typical for subgenus. Left mandible (Fig. 22e). Margin between prostheca and mola straight, with few minute denticles toward subtriangular process. Subtriangular process short. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 22d). Apex of lingua without bifid bunch of stout setae. Otherwise, as typical for subgenus. Maxilla (Fig. 22g). Maxillary palp approx. as long as galea-lacinia; palp segment II ~0.9× length of segment I. Otherwise, as typical for subgenus. Labium (Fig. 22c). Paraglossa with two spine-like setae on inner, distolateral margin. Labial palp with segment I ~0.8× length of segments II and III com- 242 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 21. Papuanatula (Fijifiliola) flowersi sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. bined. Segment II dorsally with row of five or six spine-like setae near outer, distolateral margin. Segment III elongate conical, 0.5× length of segment II, inner margin straight, outer margin convex. Otherwise, as typical for subgenus. 243 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 22. Papuanatula (Fijifiliola) flowersi sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible (detail: subtriangular process); f. Right mandible; g. Maxilla; h. Head; i. Paracercus; j. Cercus. Scale bars: 100 µm (h); 20 µm (a, c–g, i); 10 µm (b, j). 244 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 23. Papuanatula (Fijifiliola) flowersi sp. nov., larva. a. Fore leg; b. Femur, outer margin; c. Tibia; d. Tarsus, outer margin; e. Tarsus, claw; f. Abdomen; g. Abdominal terga; h. Paraproct; i, j. Tergalius IV. Scale bars: 100 µm (f); 50 µm (a); 20 µm (i); 10 µm (b–e, g, h, j). Legs (Fig. 23a–e). Ratio of leg segments: fore leg 1.0:1.0:0.5:0.2, middle leg 1.0:1.0:0.4:0.2 and hind leg 1.0:1.0:0.4:0.2. Femur. Length ~2.5× maximum width. Tibia. With row of short, blunt setae on each side parallel to row of long, 245 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands fine, simple setae. Claw with one row of 9–12 denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 23f, g). Posterior margin of terga: I–IX with triangular, pointed denticles, becoming longer toward end of abdomen. Tergalii (Fig. 23i, j). Oval; tracheation mainly limited to main trunk, dark brown; with scattered, orange-brown, hypodermal pigmentation. Margin with minute denticles and short, fine, simple setae. Paraproct (Fig. 23h). Posterior margin with prolongation, with denticles. Caudalii (Fig. 22i, j). Cerci without swimming setae. Paracercus with 13 segments. Pose of subimaginal gonostyli under larval cuticle. Unknown. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Local species; larvae living in run of fast flowing, turbulent mountain rivers with pristine water (Fig. 36d, e). Etymology. The species is dedicated to R.W. Flowers (formerly Florida A & M University, Tallahassee, USA), who pioneered the work on Fijian mayflies with his article dated 1990. Distribution. Fiji: Viti Levu (Fig. 39e). Papuanatula (Fijifiliola) gattolliati sp. nov. https://zoobank.org/A86F9447-E231-4BDA-868F-65CB2BF88677 Figs 24–26 Material examined. Holotype. FIJI • larva; Vanua Levu, Cacaudrove Prov., Seaqaqa Riv., bridge near Saivou village; 16°36'25"S, 179°08'46"E; 80 m; 05.xi.2024; leg. T. Kaltenbach; on slide; GBIFCH01581988; MZL. Paratypes. • 2 larvae; same data as holotype; on slides; GBIFCH01581983, GBIFCH01581989; MZL • 8 larvae; Vanua Levu, Cacaudrove Prov., tributary to Sekawa Riv., near Nakawaga; 16°39'55"S, 179°20'03"E; 32 m; 29.x.2024; leg. T. Kaltenbach; 1 on slide; GBIFCH01581907; 7 in alcohol; GBIFCH01581901, GBIFCH01581906, GBIFCH01582015; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. gattolliati sp. nov. from other species of Fijifiliola subgen. nov.: larva dorsally grey, abdominal segments laterally with blackish marking; femur on anterior side in basal ½ with reddish brown marking in large blank (well-developed on fore femur, less on middle femur and absent on hind femur), large dark grey band in middle area, reddish brown colour in subdistal part; labial palp segment III slightly pentagonal; paracercus with 12–14 segments. Description. Larva (Figs 24–26). Body length 2.9–4.4 mm, cerci ~1.5× body length. Colouration (Fig. 24a–c). Head and thorax dorsally grey with indistinct pattern, fore protoptera grey with dark grey margin; abdomen dorsally grey, terga III and IV darker, terga II and V–VIII darker in anterior part, abdominal segments laterally with oblique, blackish marking. Femur on anterior side in basal ½ with 252 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 28. Papuanatula (Fijifiliola) grisea sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Paracercus; i. Cercus; j. Head; k. Male mature larva, developing subimaginal gonostylus. Scale bars: 100 µm (j); 50 µm (c); 20 µm (e–h); 10 µm (b, d, i, k). 253 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 29. Papuanatula (Fijifiliola) grisea sp. nov., larva. a. Fore leg; b. Femur, outer margin; c. Tibia; d. Tarsus; e. Claw; f. Abdomen; g. Abdominal terga; h. Paraproct; i. Tergalius IV. Scale bars: 100 µm (f); 50 µm (a); 10 µm (b–e, g–i). 254 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands simple setae. Claw with one row of 10–12 denticles; one posterior setae. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 29f, g). Posterior margin of terga: I smooth, without denticles, II–IX with triangular, partly split denticles. Tergalii (Fig. 29i). Elongate oval; tracheation mainly limited to main trunk, dark brown. Margin smooth, with short, fine, simple setae. Paraproct (Fig. 29h). Posterior margin with prolongation, with split denticles. Caudalii (Fig. 28h, i). Cerci with 1–5 swimming setae in middle part. Paracercus with 10–15 segments. Pose of subimaginal gonostyli under larval cuticle (Fig. 28k). As typical for subgenus. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Larvae living in run or riffles of medium fast flowing lowland rivers (Figs 36b, c, 37b). Etymology. The species name refers to the predominant grey colour, which distinguishes it easily from the often co-occurring species P. aji sp. nov. Distribution. Fiji: Viti Levu (Fig. 40b). Papuanatula (Fijifiliola) sekawa sp. nov. https://zoobank.org/669EFAE4-F87D-4F81-8157-F6C69174B477 Figs 30–32 Material examined. Holotype. FIJI • larva; Vanua Levu, Cacaudrove Prov., tributary to Sekawa Riv., near Nakawaga; 16°39'55"S, 179°20'03"E; 32 m; 29.x.2024; leg. T. Kaltenbach; on slide; GBIFCH01581905; MZL. Paratypes. • 8 larvae; same data as holotype; 3 on slides; GBIFCH01581904, GBIFCH01581908, GBIFCH01221818; 5 in alcohol; GBIFCH01581902, GBIFCH01581903; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. sekawa sp. nov. from other species of Fijifiliola subgen. nov.: larva dorsally dark grey, abdominal tergum X reddish brown; femur on anterior side with large grey area in middle part, in basal ⅓ with dark grey, narrow, longitudinal streak in large blank, distal ⅓ reddish brown; labial palp segment III slightly pentagonal; paracercus with 12 segments; cerci with one or two swimming setae per segment in distomedial part. Description. Larva (Figs 30–32). Body length 3.6–4.1 mm, cerci broken. Colouration (Fig. 30a–c). Head, thorax and abdomen dorsally dark grey, thorax with indistinct pattern, fore protoptera dark grey; abdominal tergum I brighter, tergum X reddish brown. Femur on anterior side with large grey area in middle part, in basal ⅓ with dark grey, narrow, longitudinal streak in large blank, distal ⅓ reddish brown; femur on posterior side with dark brown distomedial marking surrounded by reddish brown colour; tibia and tarsus predominantly grey. Thorax and abdomen ventrally grey-brown, sternum X yellow-brown. Caudalii grey. Head. Antenna (Fig. 31h). Length ~1.5× head length. As typical for subgenus. Labrum (Fig. 31a, b). Length 0.5× maximum width. Otherwise, as typical for subgenus. 255 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 30. Papuanatula (Fijifiliola) sekawa sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. 256 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 31. Papuanatula (Fijifiliola) sekawa sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Head; i. Paracercus; j. Cercus. Scale bars: 100 µm (h); 20 µm (a, c–g, i); 10 µm (b, j). 257 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 32. Papuanatula (Fijifiliola) sekawa sp. nov., larva. a. Hind leg; b. Femur, outer margin; c. Tibia; d. Tarsus, outer margin; e. Tarsus, claw; f. Abdomen; g. Abdominal terga; h. Tergalius III; i. Paraproct. Scale bars: 100 µm (f); 50 µm (a); 10 µm (b–e, g–i). 258 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Right mandible (Fig. 31f). Margin between prostheca and mola straight, with minute denticles. Otherwise, as typical for subgenus. Left mandible (Fig. 31e). Margin between prostheca and mola slightly concave, with minute denticles toward subtriangular process. Otherwise, as typical for subgenus. Hypopharynx and superlinguae (Fig. 31d). As typical for subgenus. Maxilla (Fig. 31g). Maxillary palp slightly longer as galea-lacinia; palp segment II ~1.3× length of segment I. Otherwise, as typical for subgenus. Labium (Fig. 31c). Paraglossa with two spine-like setae on inner, distolateral margin. Labial palp with segment I approx. as long as segments II and III combined. Segment II dorsally with row of four or five spine-like setae near outer, distolateral margin. Segment III slightly pentagonal, 0.6× length of segment II. Otherwise, as typical for subgenus. Legs (Fig. 32a–e). Ratio of leg segments: fore leg 1.0:1.0:0.4:0.1, middle leg 1.0:1.0:0.3:0.1 and hind leg 1.1:1.0:0.4:0.1. Femur. Length ~3× maximum width. Setae on outer margin long, flattened, apically pointed. Tibia. With row of short, blunt setae on each side parallel to row of long, fine, simple setae. Claw with one row of nine or ten denticles; one posterior seta. Otherwise, as typical for subgenus. Abdomen. Terga (Fig. 32f, g). Posterior margin of terga: I smooth, without denticles, II–IX with triangular, pointed denticles. Tergalii (Fig. 32h). Elongate oval; tracheation well-developed, nearly reaching margins, dark brown; with reddish brown pigmentation around tracheation. Margin with minute denticles and short, fine, simple setae. Paraproct (Fig. 32i). Posterior margin with prolongation, with split denticles. Caudalii (Fig. 31i, j). Cerci with 1 or 2 swimming setae per segment in distomedial part. Paracercus with 12 segments. Pose of subimaginal gonostyli under larval cuticle. Unknown. Subimago. Unknown. Imago. Unknown. Egg. Unknown. Biological aspects. Larvae living in run or riffles of medium fast flowing lowland rivers (Fig. 38a). Etymology. The species is named after the Sekawa River system in Vanua Levu, where the type locality is. Distribution. Fiji: Vanua Levu (Fig. 40c). Papuanatula (Fijifiliola) tenebris sp. nov. https://zoobank.org/C3925780-999C-462E-B92A-E7A1F1F9B4D7 Figs 33–35 Material examined. Holotype. FIJI • larva; Viti Levu, Ba Prov., near Abaca village, Savuione Riv.; 17°40'07"S, 177°32'31"E; 510 m; 24.x.2024; leg. T. Kaltenbach; on slides; GBIFCH01221831, GBIFCH01581923; MZL. Diagnosis. Larva. Following combination of characters distinguishes P. tenebris sp. nov. from other species of Fijifiliola subgen. nov.: larva dorsally rather uniform blackish brown; femur on anterior side in basal ½ with dark brown, narrow, longitudinal streak in large, oblong blank (all legs), large dark grey band in distomedial 259 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 33. Papuanatula (Fijifiliola) tenebris sp. nov., larva, habitus. a. Dorsal view; b. Lateral view; c. Ventral view. Scale bars: 1 mm. 260 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 34. Papuanatula (Fijifiliola) tenebris sp. nov., larva. a, b. Labrum; c. Labium; d. Hypopharynx and superlinguae; e. Left mandible; f. Right mandible; g. Maxilla; h. Head; i. Paracercus; j. Cercus. Scale bars: 100 µm (h); 50 µm (c, e–g); 20 µm (a, d); 10 µm (b, i, j). 261 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 35. Papuanatula (Fijifiliola) tenebris sp. nov., larva. a. Middle leg; b. Femur, outer margin; c. Femur, inner margin; d. Tibia; e. Tibia, inner margin; f. Tarsus, outer margin; g. Tarsus, claw; h. Abdomen; i. Abdominal terga; j, k. Tergalius IV; l. Paraproct. Scale bars: 100 µm (h); 50 µm (a, j); 10 µm (b–g, i, k, l). 268 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Figure 40. Distribution of described species. a. Papuanatula (Fijifiliola) gattolliati sp. nov. (locations E, F); b. Papuanatula (Fijifiliola) grisea sp. nov. (locations A, B, I); c. Papuanatula (Fijifiliola) sekawa sp. nov. (location E); d. Papuanatula (Fijifiliola) tenebris sp. nov. (location C1). and later more detailed by Webb et al. (2018) for North American species: labial palp with curved outer margin, length of segment II < 2× basal width of segment III; pronotum with inverted, dark, U-shaped marking (as in the flavistriga complex); dorsal, abdominal pattern very similar to flavistriga complex; robust setae absent on antennal scape and pedicel, paraproct, tergalii, and abdominal terga; length of tergalii < 2× width, serrate margins; femur with subquadrangular, dark spot. Therefore, Baetis procul sp. nov. should be included into the subgenus Baetis s. str., as defined slightly differently by both Webb et al. (2018) and Bauernfeind and Soldán (2012), also adopted by Yaagoubi et al. (2023). The morphologically most similar species is B. taiwanensis from Taiwan and Japan. Baetis procul sp. nov. is distinguished from B. taiwanensis from Taiwan by the following character: larva with abdominal terga I–VIII grey-brown, with distinct sublateral pale areas (Figs 1a, c, 3i; in taiwanensis terga III–V much paler than I, II, VI, and VII; Müller-Liebenau 1985: fig. 7). It is distinguished from B. taiwanensis from Japan by following characters: femur of larva with irregular, medial brown spot, and subapical, yellow-brown spot (Fig. 3a; taiwanensis with rectangular, medial spot and without subapical, yellow-brown spot; Fujitani et al. 2004: figs 9, 16); larval paraproct with five or six large spines (Fig. 3m; taiwanensis with several larger and many small spines; Fujitani et al. 2004: fig. 18); hindwing of imago narrow, with concave anal margin (Fig. 4e; taiwanensis 269 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands with wider hindwing, anal margin straight; Fujitani et al. 2004: fig. 3). Judging from descriptions and figures of B. taiwanensis from Taiwan (Müller-Liebenau 1985) and Japan (Fujitani et al. 2004), it is not excluded that these are two different species, both different from B. procul sp. nov. Further morphologic and genetic investigations may be necessary to clarify their status. Three female imagos of Baetis procul sp. nov. were collected at one site by kick-sampling in the river, together with larvae of Papuanatula aji sp. nov. and P. grisea sp. nov. (location B). This suggests that the imagos were laying their eggs under water, as it is already known from other species of Baetis (Sartori and Brittain 2015; Jacobus et al. 2019). In the lab, it was discovered that none of the three imagos had any egg remaining in the abdomen, which supports the assumption that they were caught just after egg laying under water. The occurrence of a Baetis species in Fiji was unexpected, firstly because there is no species known from New Guinea and the geographic distance to other Baetis species in Taiwan and Japan is very large, and secondly, because Flowers (1990) did not mention Baetis s. str., but only three species of Baetis group molawinensis (according to Müller-Liebenau and Hubbard 1985; easily distinguishable from Baetis s. str. by their distomedial protuberance on labial palp segment II), which later became Labiobaetis. The path of colonisation of the Fiji Islands by Baetis remains speculative until more material and studies are available from other archipelagos in the South Pacific, especially from the Solomon Islands. However, several scenarios may be considered. Firstly, a colonisation from New Guinea along the Melanesian arc, which had even more islands in the past and therefore, enabled shorter dispersal distances (Flowers 1990; Ryan 2009); in this case, Baetis should be found in New Guinea in the future. New Guinea is very large and many regions are still poorly or not at all investigated for mayflies, including New Ireland (apart from Demoulin 1969). Secondly, a colonisation from Southeast Asia, where Baetis is present, via Palau to the Melanesian arc. An ecological study reported the presence of Baetis in Palau (Bright 1982). However, this could be also a species of Labiobaetis, which was still included into Baetis at this point. Finally, one cannot exclude the involvement of human activities in the arrival of Baetis on the Fiji Islands. Assignment of Fijifiliola subgen. nov. to Papuanatula, and affinities with other subgenera Fijifiliola subgen. nov. clearly belongs to the genus Papuanatula, according to the diagnosis given in Kaltenbach et al. (2025a): antennal scapes basally narrow, distally broader; labrum much wider than long; labium with glossae much shorter than paraglossae; maxillary palp with two segments; outer side of each femur usually with single regular row of long, hair-like setae; femoral patch absent on all legs; patella-tibial suture usually present on all legs; tibia-tarsal condylus (originally located on outer side) turned to anterior side; anterior (originally outer-anterior) side of each tibia usually with regular row of setae similar to that on femur; anterior (originally outer) side of each tarsus usually with regular row of setae similar to femur and tibia; tarsus usually with conspicuous, long seta subdistally on inner margin; claw with single row of denticles and one or several posterior setae; hind protoptera absent or vestigial; tergalii present on abdominal segments II–VII; paraproct usually with prolongation on proximal margin; cerci usually longer than body length; paracercus strongly reduced or vestigial. How- 270 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands ever, in Fijifiliola subgen. nov., the regular row of setae on anterior side of tibia is not similar to the one on outer margin of femur, but usually consisting of long, fine, simple setae; a row of similar setae is present along outer margin of tarsus (Fig. 5). These are the main differences to both other subgenera Papuanatula s. str. and Papuafiliola. Another important difference is the shape of the distomedial protuberance on labial palp segment II: very short and broadly rounded in Fijifiliola subgen. nov., minute or not developed in Papuanatula s. str., and well-developed, elongate in Papuafiliola (Fig. 5). Further, Fijifiliola subgen. nov. is distinguished from the other two subgenera by a different combination of some characters, as summarised in Fig. 5 and Table 3: shape of labrum is similar to that of Papuanatula s. str. (widest in middle part; widest basally in Papuafiliola); labrum with dorsal, submarginal arc of simple setae similar to Papuafiliola, but a full arc instead of few setae as in Papuafiliola (feathered setae in Papuanatula s. str.); incisor of both mandibles blade-like enlarged as in Papuanatula s. str. (not blade-like in Papuafiliola); distalmost seta on inner margin of tarsus much longer than other setae as in Papuanatula s. str. (not much longer in Papuafiliola). Overall, Fijifiliola subgen. nov. seems to have more morphological similarities with Papuanatula s. str. than with Papuafiliola, However, these similarities do not justify a judgement on the relationship between the three subgenera of Papuanatula. Based on the apomorphies and the homogeneity of all three subgenera, and their geographic distribution, raising them from subgeneric to generic status could be considered in the future. However, I prefer to remain conservative, waiting for further collections and studies on other archipelagos of the South Pacific. Parthenogenesis and ovoviviparity in Papuanatula (Fijifiliola) subgen. nov. In one mature female larva of P. (F.) claudia sp. nov., the abdomen was filled with eggs in which the developing larvae could be observed (Fig. 16k, l). It is the first documented case of parthenogenesis in Papuanatula. There are male and female larvae in this population, which means that the parthenogenesis is facultative. As the young larvae are already developing in this early phase, the species is most probably also ovoviviparous. Both, parthenogenesis and ovoviviparity are well known in mayflies (Funk et al. 2010; Sartori and Brittain 2015; Jacobus et al. 2019; Liégeois et al. 2021), a comprehensive review is given by Liégeois et al. (2021). Moreover, there is evidence that most, if not all, mayflies, an ancient group with a primitive reproductive system, are facultatively parthenogenetic (Funk et al. 2010). In many Baetidae, ovoviviparity and/or parthenogenesis have also been reported (e.g. Acerpenna Waltz & McCafferty, Alainites Waltz & McCafferty, Anafroptilum Kluge, Baetis Leach, Callibaetis Eaton, Centroptilum Eaton, Cloeon Leach, Labiobaetis, Nigrobaetis Kazlauskas (in Novikova and Kluge), Procloeon Bengtsson) (Needham and Murphy 1924; Berner 1941; Sivaramakrishnan et al. 1991; Funk et al. 2010; Gattolliat and Staniczek 2011; Kluge 2016; Liégeois et al. 2021). Parthenogenesis and ovoviviparity may favour successful random colonisation, because it enables virgin females to form populations in new habitats, which may even be bisexual (Funk et al. 2010). Therefore, it is not surprising to find it in species living in remote, isolated environments like islands or archipelagos, as it is the case for Papuanatula (F.) claudia sp. nov. from Fiji and Labiobaetis paradisus Gattolliat & Staniczek from Vanuatu (Gattolliat and Staniczek 2011). 271 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Genetics COI barcode sequences were obtained from eight of the ten species of Fijifiliola subgen. nov. (Table 1; Suppl. material 1). The interspecific distances are always rather high (13%–23%, K2P), in line with genetic distances found in Papuanatula (incl. Papuanatula s. str. and Papuafiliola) in New Guinea (10%–25%; Kaltenbach et al. 2025a, b). Labiobaetis Novikova & Kluge has also comparable genetic distances in New Guinea (13%–31%; Kaltenbach and Gattolliat 2018, 2021). Ball et al. (2005) reported a mean interspecific, congeneric distance of 18% for mayflies from the United States and Canada. The intraspecific distances were mostly between 0% and 3%, as expected. An exception is one specimen of P. aji sp. nov. from location D with 6%–7% genetic distance to all other locations, whereby, another specimen of the same location has the usual 0%–3%. Isolation cannot be an explanation for this case, but rather the involvement of a pseudogene or other unknown reasons. The second exception is one specimen of P. bula sp. nov. from location D1 with 5%–6% genetic distance to the other locations. Here, the larger genetic distance could be explained by a possible isolation from the other locations. Apart from these two exceptions, the species of Fijifiliola subgen. nov. do not show distances of more than the usual 0%–3% between different locations of the same species, even not between the islands Viti Levu and Vanua Levu (P. aji sp. nov.). Intraspecific distances of 4%–6% were also reported in some cases for Labiobaetis species in New Guinea, Indonesia, and Borneo (Kaltenbach and Gattolliat 2018, 2019, 2020), as well as in aquatic beetles in the Philippines (Komarek and Freitag 2020). Ball et al. (2005) also reported a case with 6% intraspecific distance in a mayfly in North America. Moreover, in a large study on the DNA barcode (COI) of North American Ephemeroptera, nearly 20% of the species included two or three haplotype clusters with more than 5% sequence divergence (Webb et al. 2012). The likely involvement of species complexes underlying these results are discussed in this study. Finally, intraspecific K2P distances of more than 3.5% are not uncommon within Plecoptera as well (Gill et al. 2015; Gattolliat et al. 2016). Distribution and diversity of Papuanatula Based on present data, the genus has a disjunct distribution in New Guinea (incl. New Britain), the island of Sulawesi, and in the Fiji Islands (Kaltenbach et al. 2025a, b; this study). The subgenus Papuanatula s. str. is present in New Guinea and Sulawesi, Papuafiliola in New Guinea, and Fijifiliola in the Fiji Islands only. Despite many collection activities and studies on Baetidae in continental Southeast Asia, Indonesia, and the Philippines in recent years, no species of Papuanatula was found apart from in Sulawesi. However, the mayfly fauna of islands between Sulawesi and New Guinea (e.g. Ambon, Halmahera) is still very poorly studied. Islands or archipelagos of the South Pacific other than Fiji Islands (e.g., Solomon Islands, Tonga, Samoa) are mostly very poorly or not at all studied and no Papuanatula species were reported from there (Tillyard 1928). From Vanuatu, which was studied in more detail, only a very low diversity was reported and no species of Papuanatula were recorded (Gattolliat and Staniczek 2011). New Caledonia is an exception and much better studied, with 272 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands a high diversity of Leptophlebiidae and one species of Cloeon of unclear origin, but no species of Papuanatula (Peters and Mary 2016; Hrivniak et al. 2023 and citations therein). The fact that all known species of Papuanatula in Fiji belong to the morphologically well-defined subgenus Fijifiliola subgen. nov., which was not discovered anywhere else so far, speaks for one single colonisation by a Papuanatula species in the past, with subsequent local radiation. However, the morphology of Fijifiliola subgen. nov. with characters partly similar to Papuanatula s. str. and partly to Papuafiliola (Fig. 5; Table 3), does not allow an assessment on whether Fijifiliola subgen. nov. is more related to one or the other of these subgenera. Flowers (1990) already recognised the relationship of Fijifiliola subgen. nov. (as New Genus “A”) with two undescribed species from New Guinea and one from New Britain (“Pseudocloeon B” from “Bismarck Islands”; Demoulin 1969), which were later described as Papuanatula species by Lugo-Ortiz and McCafferty (1999). Flowers (1990) mentioned eight different species, one of them very common (probably P. aji sp. nov.) and some occurring in one locality only, based on rich material from 60 different locations on four islands, mostly from the main islands Viti Levu and Vanua Levu. In this study, ten species are described from 12 different sites of nine different rivers on Viti Levu and Vanua Levu. This suggests that there are probably more than eight species in the material studied by Flowers (1990), which may be revealed by further taxonomic investigation of this material, and that there is a total of more than the ten species described in this study. This is a remarkable diversity for this archipelago, which could be explained by the highly structured environment (islands and mountainous areas), providing opportunities for random colonisation, followed by isolation and speciation. Allopatry was identified as main mechanism of diversification of the megadiverse Dytiscidae genus Exocelina Balke, 1998 in New Guinea (see discussion in Kaltenbach et al. 2025a; Toussaint et al. 2013, 2014), and could be also the driver of the diversity in the Fiji Islands. Further collections on the main islands Viti Levu and Vanua Levu, especially in higher parts of mountainous areas, and on yet unexplored islands such as Taveuni (third biggest island), will most probably uncover further new species of Papuanatula (Fijifiliola) subgen. nov. in the Fiji Islands. Acknowledgements I cordially thank my wife Claudia Kaltenbach for her constant support and a helping hand during field work. Further, I am appreciative to AJ, the owner of the Outback Hotel on Viti Levu for his support and company of the field work in the Ba Province. I am also grateful to Céline Stoffel (Muséum cantonal des Sciences Naturelles, Lausanne, Switzerland; MZL) for her support with lab work and preparation of the COI barcodes, and to Jean-Luc Gattolliat (Muséum cantonal des Sciences Naturelles, Lausanne, Switzerland; MZL) for helpful information and fruitful discussions. Finally, I am thankful to the reviewers for their valuable comments and corrections. Additional information Conflict of interest The author solely contributed to this work. 273 ZooKeys 1259: 205–276 (2025), DOI: 10.3897/zookeys.1259.168521 Thomas Kaltenbach: Mayflies of Fiji Islands Ethical statement No ethical statement was reported. Use of AI No use of AI was reported. Funding No funding was reported. Author contributions The author solely contributed to this work. 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ZooKeys 794: 45–84. https://doi.org/10.3897/zookeys.794.28214 Supplementary material 1 Supportive Data: Genetic distance (COI, K2P; intraspecific distances in bold) Author: Thomas Kaltenbach Data type: xls Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/zookeys.1259.168521.suppl1