A new genus and three new species of the subfamily Phygadeuontinae (Hymenoptera: Ichneumonidae) from northern Vietnam

236 European Journal of Taxonomy 1026: 236–249 https://doi.org/10.5852/ejt.2025.1026.3119 europeanjournaloftaxonomy.eu ISSN 2118-9773 2025 · Pham N.T. & Cao N.T. This work is licensed under a Creative Commons Attribution License (CC BY 4.0) Received: 20 May 2025 • Accepted: 16 September 2025 • Published: 21 November 2025 Topic editor: Tony Robillard • Section editor: Gavin Broad • Desk editor: Lizeth Alonso Research article urn:lsid:zoobank.org:pub:AE8A88D7-28DE-4973-AEB2-2751D5D0A9F5 A new genus and three new species of the subfamily Phygadeuontinae (Hymenoptera: Ichneumonidae) from northern Vietnam Nhi Thi PHAM1,* & Nga Thi Quynh CAO2  1,2 Institute of Biology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam. * Corresponding author: [email protected] 2 Email: cqnga1[email protected] Abstract. A new Darwin wasp genus, Longipectus gen. nov., is described from northern Vietnam to include three new species Longipectus hagiangensis gen. et sp. nov., Longipectus planus gen. et sp. nov., and Longipectus yagi gen. et sp. nov. Morphologically, the new genus Longipectus differs from other phygadeuontine genera by the combination of the globular head, the long mesosoma, the long notauli, theshortfirsttergite,andthelongitudinalwrinklesonthefirstandsecondtergites. Key words. Darwin wasp, parasitoid, taxonomy. Pham N.T. & Cao N.T.Q. 2025. A new genus and three new species of the subfamily Phygadeuontinae (Hymenoptera: Ichneumonidae) from northern Vietnam. European Journal of Taxonomy 1026: 236–249. https://doi.org/10.5852/ejt.2025.1026.3119 Introduction The subfamily Phygadeuontinae Förster, 1869 consists of 125 genera with nearly 2000 species worldwide (Yu et al. 2016; Santos 2017; Pham et al. 2019; Reshchikov et al. 2019; Pham et al. 2020; Watanabe 2021; Pham et al. 2024; Lima & Fernandes 2024). This subfamily is most diverse in temperate regions and can be distinguished from the closely related Cryptinae by usually smaller body size, forewing cross-vein 2m-cu usually distinctly inclivous with two bullae, and the sternaulus ending above the ventroposterior corner of the mesopleuron (Santos 2017). Members of Phygadeuontinae parasitize small cocoons or cocoon-like structures. Cocoons of many holometabolous insect groups have been recorded as hosts of phygadeuontine species such as Lepidoptera, Hymenoptera, Coleoptera, Diptera, as well as egg sacs of spiders. Some species are also recorded as secondary parasitoids (Townes 1970; Wahl & Sharke 1993). Since the seminal work of Townes (1970), no less than 20 genera and more than 650 species have been described as new within this subfamily, of which two genera and 84 species were discovered from the Oriental region (Yu et al. 2016; Pham et al. 2019, 2020, 2024; Reshchikov et al. 2019; Watanabe 2021; Lima & Fernandes 2024). That means taxonomic studies of Phygadeuontinae, particularly in the Oriental regions, are tremendously PHAM N.T. & CAO N.T.Q., Longipectus, a new genus of Ichneumonidae from Vietnam 237 scarceandinvaluable.ThisworkaimstodescribeanewgenusofPhygadeuontinae,thefirstforthe Oriental region since the discovery of the genus Carinityla Sheng & Sun, 2010, and to propose three new species on the basis of specimens from northern Vietnam. Material and methods Thousands of ichneumonid wasps were collected in northern Vietnam from 2013 to 2024 by Malaise traps and sweep nets, however, very few specimens are used in this study due to their scarcity in our scientificcollection;TheyaredepositedattheInstituteofBiology(IB),VietnamAcademyofScience and Technology, Hanoi, Vietnam. Morphological terminology follows Broad et al. (2018). Photographs were taken with a Nikon SMZ800N M80 stereo microscope and an Olympus SZX 16 stereo microscope, and subsequently stacked with Helicon Focus. Abbreviations used in text F1, F2, F3, ...Fn = Flagellomere 1st, 2nd, 3rd, ...n T1, T2, T3, ...Tn = Metasomal tergite 1, 2, 3, ...n Results Taxonomy Class Insecta Linnaeus, 1758 Order Hymenoptera Linnaeus, 1758 Superfamily Ichneumonoidea Latreille, 1802 Family Ichneumonidae Latreille, 1802 Subfamily Phygadeuontinae Förster, 1869 Genus Longipectus gen. nov. urn:lsid:zoobank.org:act:8FAC47A8-F666-4044-BB19-D9629A32A299 Diagnosis Head globular; occipital carina widely separated from posterior ocelli, ventrally meeting hypostomal carina about 0.6–1.0 × basal mandibular width from base of mandible; mesosoma elongate and dorsoventrally compressed, 0.7–0.8 × as long as metasoma, with notauli distinct on anterior 0.5–0.7 of mesoscutum; mesopleuron with episternal scrobe connected to mesopleural furrow by a groove; posterior transeverse carina of mesosternum short and v-shaped; propodeum with area petiolaris separated from areasuperomediawhenthelatterdefined;firsttergiteshort,about0.4–0.7× as long as second tergite, withventrolateralcarinacomplete;firstandsecondtergiteswithlongitudinalwrinkles;metasomal tergites 2 and 3 with laterotergite separated by distinct suture; ovipositor relatively slender. Etymology The name of the new genus is derived from the Latin words ‘longus’, meaning ‘long’, and ‘pectus’, meaning ‘thorax’, referring to its long thorax. Gender: masculine. Type species Longipectus yagi gen. et sp. nov. European Journal of Taxonomy 1026: 236–249 (2025) 238 Description Head globular. Occipital carina thickened, complete and widely separated from posterior ocelli, ventrally meeting hypostomal carina about 0.6–1.0 × basal mandibular width from base of mandible. Face as high as wide to higher than wide. Clypeal suture indistinct. Mandible short, 2.0–2.5 × as long as median width, weakly to distinctly narrowed towards apex, teeth sharp. Maxillary palp long to moderately long, reachinganteriortocenterpartofmesopleuron.Basalflagellomereslongandnarrow,F17.0–11.0× as long as wide. Mesosoma 0.7–0.8 × as long as metasoma. Pronotum 0.3–0.4 × as long as mesosoma, epomia absent or present as a short stub, dorso-medially of pronotum, just behind pronotal collar without or with weak median carina. Mesoscutum 1.2–1.9 × as long as maximum width. Notauli distinct on anterior 0.5–0.7 of mesoscutum. Scutellum weakly to moderately convex, lateral carina present basally. Mesopleuron with epicnemial carina present ventrally or dorsally, sternaulus present or absent, episternal scrobe connected to mesopleural furrow by a groove. Posterior transverse carina of mesosternum short and v-shaped. Propodeum gradually sloping in lateral view, area petiolaris separated from area superomediawhenthelatterdefined,propodealspiraclesmallandround.T1short,0.4–0.7× as long as T2, polished, dorsolateral and ventrolateral carinae distinct. T1–T2 with longitudinal wrinkles. T2–T3 with laterotergites separated by distinct sutures. Ovipositor thin, straight, lower valve with teeth apically. Ovipositor sheath 0.18–0.38 × as long as hind tibia length. Legs long, hind femur 5.3–6.2 × as long as wide, hind tarsus longer than hind tibia, hind basitarsus nearly 0.5 × as long as hind tarsus. Fore wing length 3.5–5.1 mm, vein 3rs-m absent, vein 2m-cu inclivous, with two bullae. Key to species of Longipectus gen. nov. 1. Mesosoma extremely elongate, 0.8 × as long as metasoma (Fig. 6); pronotum 0.4 × as long as mesosoma (Fig. 7E); propodeum with densely transverse striations dorsally (except smooth posteriorly), area superomedia absent, posterior transverse carina forming a crest (Fig. 7H); fore wing smoky medially (Figs 6, 7G) …………………………………L. yagi gen. et. sp. nov. – Mesosoma less elongate, about 0.7 × as long as metasoma (Figs 1, 3); pronotum 0.3 × as long asmesosoma(Figs2E,4E);propodeumpunctatetomatt,areasuperomediaweaklydefinedor open laterally, posterior transverse carina normal; fore wing hyaline (Figs 2G, 4G) ………….2 2. Antenna with normally cylindrical flagellomeres; sternaulus distinct, reaching hind margin of mesopleuron (Fig. 2E); propodeum matt, area superomedia weakly defined (Fig. 2H); ovipositor sheath 0.33–0.38 × as long as hind tibia length…...L. hagiangensis gen. et. sp. nov. –Antennawithposteriorflagellomeresthickenedandflattenedventrally;sternaulusindistinct (Fig. 4E); propodeum punctate, area superomedia open laterally (Fig. 4H); ovipositor sheath 0.18–0.19 × as long as hind tibia length ………................................ L. planus gen. et. sp. nov. Longipectus hagiangensis gen. et sp. nov. urn:lsid:zoobank.org:act:C13A91A0-2DBD-4C3B-9F28-99C27C631FEE Figs 1–2 Diagnosis Sternaulusdistinct,reachinghindmarginofmesopleuron;areasuperomediaweaklydefined;ovipositor sheath 0.33–0.38 × as long as hind tibia. Etymology Thespecificnamereferstoitstypelocality,HaGiangProvince. PHAM N.T. & CAO N.T.Q., Longipectus, a new genus of Ichneumonidae from Vietnam 239 Type material Holotype VIETNAM•♀;HaGiangProvince,QuanBadistrict,TungVaicommune;23°03ʹ18ʺN,104°50ʹ44ʺE; 1340 m a.s.l.; 26 Mar.–14 Apr. 2024; N.T. Pham leg.; Malaise trap; IB. Paratypes VIETNAM•1♀;CaoBangProvince,PhiaOac-PhiaDenNationalPark;8–18May2013;T.H. Phamleg.;Malaisetrap;IB.•2♀♀;HaGiangProvince,MeoVacdistrict,ChiSan;23°09.53ʹN, 105°25.023ʹE;1149ma.s.l.;1Apr.–31May2024;N.T.PhamandN.T.Q.Caoleg;Malaisetrap; IB. Description Female Head. Face 1.0 × as wide as high, granulate, with setae. Clypeal suture indistinct. Clypeus 2.0 × as wide as high, polished, sparsely punctate, with setae, ventral margin weakly impressed. Mandible short and stout, 2.4 × as long as median width, weakly narrowed towards apex, teeth sharp, upper tooth longer than lower tooth. Malar space granulate, 0.7 × as wide as mandibular basal width (Fig. 2A). Gena matt, with setae. Frons and vertex mat, with setae. Postero-ocellar distance 1.2 × ocular-ocellar distance, 0.8 × medianocellusdiameter(Fig.2B).Antennawith32flagellomeres,F17.0×aslongaswide,1.1×as long as F2. Occipital carina complete, ventrally meeting hypostomal carina about 0.6 × basal mandibular width from base of mandible. Fig. 1. Longipectus hagiangensisgen.etsp.nov.,holotype,♀ (IB), habitus, lateral view Scale bar = 1 mm. European Journal of Taxonomy 1026: 236–249 (2025) 240 Fig. 2. Longipectus hagiangensisgen.etsp.nov.,holotype,♀ (IB). A. Head, frontal view. B. Head, dorsal view. C. Head, lateral view. D. Mesonotum. E. Mesosoma, lateral view. F. Metasomal tergites. G. Wings. H. Propodeum. K. Ovipositor. Scale bars: A–F, K = 0.2 mm; G = 0.5 mm. PHAM N.T. & CAO N.T.Q., Longipectus, a new genus of Ichneumonidae from Vietnam 241 MesosoMa. 0.7 × as long as metasoma (Fig. 1). Pronotum 0.3 × as long as mesosoma, matt dorsally, posterior corner punctostriate, with setae, medially strongly impressed, subpolished, with striations. Epomia absent (Fig. 2E). Mesoscutum 1.4 × as long as its maximum width, granulate. Notauli present on anterior0.5ofmesoscutum.Scutellummoderatelyweaklyconvex,finelygranulate,exceptimpunctate posteriorly, lateral carina present basally (Fig. 2D). Mesopleuron matt, punctate, with setae; epicnemial carina distinct on ventral 0.7 of mesopleuron. Sternaulus distinct, reaching hind margin of mesopleuron, distinctly dorsal of lower posterior . Metapleuron matt. Juxtacoxal carina complete (Fig. 2E). Propodeum graduallyslopinginlateralview,matt,exceptareapetiolarissmooth.Areasuperomediaweaklydefined, separated from area petiolaris (Fig. 2H). Spiracle small, round. Wings. Fore wing length ca 3.6 mm, vein 1cu-a postfurcal to M&RS, curved, vein 3rs-m absent, vein 2rs-m slightly longer than length of M between 2rs-m and 2m-cu, length of CU between 1m-cu&M and 2cu-a 1.1 × length of 2cu-a. Hind wing with distal abscissa of CU present, length of CU between M and cu-a 1.3 × length of cu-a. Legs. Hind coxa matt. Hind femur 5.6 × as long as its maximum width, 0.8 × as long as hind tibia length. Hind tarsus 1.2 × hind tibia. Hind basitarsus 0.48 × as long as tarsus. MetasoMa. T1 and T2 subpolished, with longitudinal wrinkles, T3 matt, with longitudinal wrinkles onanterior0.75,T4onwardsfinelypunctate.T12.5× as long as posterior width, ventrolateral carina distinct; spiracle small, round. T2 1.5 × as long as T1, 2.9 × as long as anterior width, 1.5 × as long as posterior width (Fig. 2F). Ovipositor thin, straight, lower valve with teeth apically (Fig. 2K); ovipositor sheath 0.33 × as long as hind tibia. CoLour. Black with reddish brown markings. Head black, scape ventrally and mandible reddish brown, palpi yellow. T2–T5 reddish brown apically, T6 onward reddish brown. Fore and mid legs reddish brown, except coxae, trochanters, trochantelli yellow. Hind leg largely black except trochanter and trochantellus yellow. Wings hyaline, wing veins brown. Variation Paratypes with malar space from 0.6–0.8 × as long as mandibular basal width, mandible 2.0–2.5 × as long as median width, hind femur varies from 5.3–5.6 × as long as wide, 0.85–0.9× as long as hind tibia, T1 2.3–2.5 × as long as posterior width, T2 2.7–2.8 × anterior width, 1.4 × posterior width, ovipositor sheath 0.35–0.38 × hind tibia length. Paratype collected from Cao Bang Province has postero-ocellar distance 1.3 × ocular-ocellar distance, 1.0 × median ocellus diameter, fore wing 3.8 mm long, length of hind wing vein CU between M and cu-a 0.9 × length of cu-a. Male Unknown. Distribution Currently known only from evergreen montane forests in Ha Giang and Cao Bang provinces, northeastern Vietnam. European Journal of Taxonomy 1026: 236–249 (2025) 242 Longipectus planus gen. et sp. nov. urn:lsid:zoobank.org:act:56890433-4028-410E-A0C3-0F49424F2BED Figs 3–5 Diagnosis AntennawithF9onwardsthickenedandflattenedventrally;sternaulusindistinct;areasuperomediaopen laterally; ovipositor sheath 0.18–0.19× as long as hind tibia. Etymology Thespecificname‘planus’isaLatinadjectivemeaning‘flat’,referringtoitsdistallyflattenedantenna. Type material Holotype VIETNAM•♀;CaoBangProvince,PhiaOac-PhiaDenNationalPark;22°36ʹ12ʺN,105°53ʹ10ʺE; 980 m a.s.l.; 30 Apr. 2022; D.D. Tran leg.; Malaise trap; IB. Paratypes VIETNAM•1♀;HoaBinhProvince,MaiChaudistrict,HangKiacommune;1400ma.s.l.;10Oct. 2019;LongD.K.leg.;sweepnet;IB•1♂;SonLaProvince,ThuanChaudistrict,CoMacommune; 21°19ʹ2.2ʺN,103°35ʹ14.1ʺE; 1,591 m a.s. l.; 27 Apr.–2 May 2016; T.V. Hoang and B.V. Nguyen leg.; Malaise trap; IB. Fig. 3. Longipectus planus gen.etsp.nov.,holotype,♀(IB),habitus,lateralview.Scalebar=1mm. PHAM N.T. & CAO N.T.Q., Longipectus, a new genus of Ichneumonidae from Vietnam 243 Fig. 4. Longipectus planus gen.etsp.nov.,holotype,♀(IB).A. Head, frontal view. B. Head, dorsal view. C. Head, lateral view. D. Mesonotum. E. Mesosoma, lateral view. F. Metasomal tergites. G. Wings. H. Propodeum. K. Ovipositor. Scale bars: A–E, H–K = 0.2 mm; F–G= 0.5 mm. European Journal of Taxonomy 1026: 236–249 (2025) 244 Description Female Head. Face 0.8 × as wide as high, granulate, with setae. Clypeal suture indistinct. Clypeus 1.7 × as wide as high, similar sculptures as face, ventral margin weakly impressed. Mandible short, 2.5 × as long as median width, gradually narrowed towards apex, teeth sharp, upper tooth longer than lower tooth. Malarspacefinelygranulate,0.4×aswideasmandibularbasalwidth(Fig.4A).Gena,fronsandvertex finelygranulate,withsetae.Postero-ocellardistance0.9×ocular-ocellardistance,0.8×medianocellus diameter(Fig.4B).Antennawith26flagellomeres,F19.0×aslongaswide,1.2×aslongasF2,ventral sideofF9onwardsflattenedandthickened.Occipitalcarinacomplete,ventrallymeetinghypostomal carina about 1.0 × basal mandibular width from base of mandible. MesosoMa.0.7×aslongasmetasoma(Fig.3).Pronotum0.3×aslongasmesosoma,polished,finely granulate anteriorly and posteriorly, medially strongly impressed, smooth. Epomia short (Fig. 4E). Mesoscutum 1.5 × as long as its maximum width, granulate. Notauli present on anterior 2/3 of mesoscutum.Scutellummoderatelyconvex,finelygranulate,exceptimpunctateposteriorly,lateral carinapresentbasally(Fig.4D).Mesopleuronfinelygranulate,withsetae;epicnemialcarinadistinct onventral0.7ofmesopleuron.Sternaulusindistinct.Metapleuronfinelygranulate.Juxtacoxalcarina absent (Fig. 4E). Propodeum gradually sloping in lateral view, punctate dorsally, smooth at level of area superomediaandareapetiolaris.Areasuperomediaopenlaterally.Areapetiolarisdefined(Fig.4H). Spiracle small, round. Wings. Fore wing length ca 4.1 mm, vein 1cu-a interstitial to M&RS, weakly curved ventrally, vein 3rs-m absent, vein 2rs-m slightly longer than length of M between 2rs-m and 2m-cu, length of CU Fig. 5. Longipectus planusgen.etsp.nov.,paratype,♂(IB). A. Habitus, lateral view. B. Head, frontal view. C. Head, dorsal view. D. Propodeum. E. Mesoscutum. Scale bars: A = 1 mm; B–E = 0.2 mm.