A colony of Camponotus nicobarensis Mayr, 1865 (Hymenoptera: Formicidae) nesting in teapots: just an anecdotal 'nature curiosity' or also a warning against possible ant invasiveness?

1 ANNALS OF THE UPPER SILESIAN MUSEUM IN BYTOM ENTOMOLOGY Vol. 34 (online 011): 1–11 ISSN 0867-1966, eISSN 2544-039X (online) Bytom, 03.11.2025 Wojciech Czechowski1 , Maksymilian Wiśniewski2, Gema TrigosPeral1 A colony of Camponotus nicobarensis Mayr, 1865 (Hymenoptera: Formicidae) nesting in teapots: just an anecdotal ‘nature curiosity’ or also a warning against possible ant invasiveness? https://doi.org/10.5281/zenodo.17511589 1 Museum and Institute of Zoology, Polish Academy of Sciences, Twarda 51/55, 01-818 Warsaw, Poland, e-mail: [email protected].pl, ORCID: 0000-0002-1285-3700 (WC); 0000-0002-8713-5703 (GTP) 2 Wiejska St 9/40, 00-840 Warsaw, Poland Abstract: Camponotus nicobarensis Mayr is an oriental ant species, very popular among amateur ant breeders and easily available in online stores worldwide. At the same time, paradoxically, the professional myrmecological literature offers very little information about its biology or ecology. This report presents the case of a colony of C. nicobarensis kept in a home breeding facility in Warsaw, which escaped from a formicarium it had occupied for several years and, upon exploring the flat, voluntarily chose to relocate its nest into an empty ceramic teapot. Eight months later, the entire colony spontaneously moved to another teapot standing next to it. In each of these vessels, the queen laid eggs and full development of the offspring took place there, which testifies to an extraordinary nesting plasticity and considerable adaptability of the species. After five consecutive months, when the colony size had increased significantly, a group of workers with a large number of larvae moved back to the previously inhabited teapot, creating a branch nest there. The ants were nocturnal, searching the apartment (mainly the kitchen) for food; in the summer, they also ventured out onto the balcony. Based on these observations we drew attention to the possible adverse effects of the mass and virtually unrestricted online trading of exotic ants worldwide as potentially invasive species. These dangers can be particularly grave when insufficient knowledge about the species’ biology makes it difficult to assess the true invasive potential of species being traded. Key words: adaptability, ant keeping, ant trade, atypical nests, biological invasions, ecological plasticity, flexibility of nesting. 2 INTRODUCTION In the wild, ants nest in a manner specific to a given species (or group of species) with regard to the choice of nest substrate and location as well as the building material. However, there are deviations from these evolutionarily fixed standards – accidental or caused by some unique specifics of local habitat conditions – which indicate the eco-ethological adaptability of the species. Examples of deviations from the typical nest substrate and location include: (1) Lasius niger (L.) – a species that normally nests in the soil – nesting under the Styrofoam insulation of residential buildings (Czechowski 2024, 2025, J. Heinze, pers. comm. to WCz), (2) Myrmica rugulosa Nyl. nesting in the fruiting body of the cauliflower mushroom (Sparassis crispa), the structure of which resembles that of a cartoon nest of dendrophilic ants Lasius fuliginosus (Latr.) (Czechowski 1979), (3) Formica polyctena Först. nesting high up a tree in a hole filled with nesting material typical of the above-ground mounds of wood ants (E. J. Godzińska, pers. comm. to WCz). Further examples of the same include (4 and 5) nests of ants in piles of old waste paper abandoned in the habitat, the layers of which provided a humidity and temperature gradient appropriate for the individual stages of ant offspring. This type of nesting has been seen in Formica fusca L. and Lasius niger (in both cases, large-sized colonies) (Czechowski 1979, WCz, unpubl., respectively). It may also happen that ants will use some substitute material to build their nest or its mound, i.e. the above-ground part. Especially spectacular are the mounds of wood ants (subgenus Formica s. str.). Typically, such mounds are made of dry plant debris, most readily available in the vicinity of the nest (small sticks or twigs, bits of bark, fallen conifer needles, birch infructescence, etc.). Sometimes, the mound material is uncharacteristic or even artificial. Grit mounds in Formica pratensis Retz. are encountered fairly often near sandy or gravelled roads (Wuorenrinne 1994, WCz, unpubl.). A mound of F. polyctena composed largely of sawdust (almost white) was seen near a sawmill site (WCz, unpubl.). Unusual mounds of F. aquilonia Yarr. were described by Wuorenrinne (1994): (1) a mound near a bus stop covered with burnt matches, (2) a mound near a skeet shooting track covered with a 1 cm layer of shot, and (3) several mounds covered with a glittered layer of plastic balls near an industrial plant throwing away small shiny plastic pearls as waste. Ants can also use larger artifacts found in the habitat for their nesting purposes. An example would be a nest of Formica sanguinea Latr. established under the bottom of a large broken glass jar disposed of in the forest which served ants as a sun-heated incubator for pupae (WCz, unpubl.). Empty containers (glass and plastic bottles, beverage cans, etc.) representing trash in the habitat are also used as nest sites by various ground and litter ants, such as Myrmica rubra (L.), M. ruginodis Nyl., Temnothorax crassispinus (Karaw.), Formica fusca L., Lasius niger, and L. platythorax Seifert (Kolenda et al. 2020, Zięcina et al. 2025; see also Michlewicz & Tryjanowski 2017). Anyway, all the above cases of unusual ant nesting practices do not compare in terms of ‘strangeness’ to the nesting method of a home-kept colony of Camponotus nicobarensis Mayr described below. THE SPECIES Camponotus (Tanaemyrmex) nicobarensis is a subtropical oriental carpenter ant species whose range includes India (Andaman and Nicobar Islands as a typical locality), Bangladesh, Myanmar (Burma), the Indochina Peninsula (Thailand, Laos, Vietnam), the Malay Peninsula, Singapore Islands, Taiwan, and southern China (see AntMaps; Guénard et al. 2017, Janicki et al. 2016). Besides this Southeast Asian region, native to C. nicobarensis, two 3 North American locations (in USA) were also assigned to this species based on old museum specimens – later deemed erroneous due to misidentifications (AntMaps; Guénard et al. 2017, Janicki et al. 2016). In nature, C. nicobarensis is common in forest and thicket environments, nesting in dead tree trunks, pieces of rotting wood, bamboo stems, and even under stones (H. Bharti, pers. comm. to GT-P). It forms monogynous or polygynous colonies numbering from several thousand to about 20,000 adults. Due to their attractive appearance (colouration, size and polymorphism of workers), high resistance to unfavourable habitat conditions, nesting plasticity, rapid colony development, and general ease of breeding [including a possibility of living in formicaries of all types (earthen wooden, cork, plaster, concrete, acrylic) and no need for hibernation], these ants are extremely popular among amateur ant keepers. They are especially recommended online by sellers and experienced ant breeders as the first exotic ant species (see e.g. The Wild Martin 2021). Incidentally, the scarcity of literature on the biology of such a common species is surprising. Practically the only available sources of such knowledge are the websites of online stores that trade in ants and internet forums of amateur ant keepers. The purpose of this communication is to draw attention to possible threats related to the free (although legal) trade in exotic species of ants (and not only ants) conducted by specialised online stores. The occasion for this is the case of a particularly spectacular nesting of a C. nicobarensis colony acquired from such a source and kept at home. This case perfectly illustrates the extraordinary adaptability of this species to even completely unusual habitat conditions and its nesting flexibility. The correctness of the species identification was confirmed with the key in the paper by Dhadwal & Bharti (2023). MATERIAL The colony of C. nicobarensis, purchased online, arrived in a two-room flat in Warsaw in October 2019. At that time, it was an incipient colony consisting of one queen, a few workers and a small egg deposit. On site, the colony, initially placed in a test tube, was settled in a horizontal glazed concrete formicarium connected to the arena. In April 2021, the queen died. At that time, the colony numbered about 25 workers. Five days after the queen's death, a newly acquired queen was introduced to the arena and subsequently taken into the formicarium by resident workers. Once inside, the new queen was accepted without any problems by the orphaned colony and began laying eggs. In 2023, the first major workers began to appear in the colony. DESCRIPTION OF OBSERVATIONS After nearly five years in the formicarium, in July 2024, the entire colony, including the queen and offspring, exited the formicarium and relocated into a stand under a flower pot and partly into the soil in the pot, entering through a hole in the bottom. The circumstances of the move remain unknown, because it took place overnight (C. nicobarensis are mainly nocturnal ants). After about a month, the entire colony moved again, this time from the windowsill in the room to the kitchen, where it took up residence in an empty ceramic teapot Bulgarian-style) standing on the kitchen counter; the entrance to the nest was the spout of the teapot (Figs 1 and 2). It should be assumed that this move must have been preceded by a long nighttime exploration of the flat in search of a suitable nest locus. The move itself also took place during one night. 4 Fig. 1. Interior of the Bulgarian-style teapot occupied by the colony of C. nicobarensis (the piece of cork visible at the bottom was placed there after the ants moved in) (February 25, 2025; photo by M. Wiśniewski). Fig. 2. The spout of the Bulgarian-style teapot serving as a nest entrance (February 25, 2025; photo by M. Wiśniewski). 5 After more than eight months of living in the teapot, in early April 2025, the colony – for reasons known to themselves – moved (again overnight) into another empty ceramic teapot (Japanese-style) standing about 1 m away from the former one (Figs 3 and 4); as before, the spout of the teapot became the nest entrance (Fig. 5). Two possible reasons for this move come to mind: (1) the surfaces (both outside and inside) of the new teapot were not as slippery as the previous one, which can be seen in the photos (see Figs 1 and 2 vs Figs 3 and 5), making it easier for the ants to move around across them, and (2) the proximity of the sink as the primary water source available to the colony (Fig. 3). Immediately after this move, the number of eggs laid by the queen increased noticeably. In May 2025, the colony consisted of a queen, about 250 adult workers (minor, media and major forms; number calculated based on photos) and numerous offspring in all stages of development (from eggs to pupae) (Figs 5 and 6). After five consecutive months, at the turn of August and September when the colony size had increased significantly (two to three times; Fig. 7), a group of several dozen workers (mainly minor and media forms) with a large number of larvae of all stages moved back to the previously inhabited Bulgarian-style teapot, creating a branch nest there (Fig. 8). Thus, a two-nest colony was created, composed of a queen-right main nest (in a Japanese-style teapot) and a queenless auxiliary nest (in a Bulgarian-style one). The ants feed, as happens in the kitchen, on particles of various food (including those intentionally left for them); they also use honey baits. An important source of protein food came from the remains of prepared food and raw meat left by the cat in the cat bowl on the floor under the counter with the teapots, and later, the larvae of mealworms. The ants foraged only at night, missing the household members in time. In the summer, they also ventured out onto the balcony, where they likely visited aphids on potted plants. Fig. 3. The Japanese-style teapot inhabited by the colony of C. nicobarensis; the edge of a sink – the presumed main water source for the colony – is visible right next to it on the left (photo by M. Wiśniewski). 6 Fig. 4. Location of the both teapots successively occupied by the colony of C. nicobarensis on a kitchen counter (first one on the right, second one on the left) (photo by M. Wiśniewski). Fig. 5. Interior of the Japanese-style teapot occupied by the colony of C. nicobarensis with the visible inner opening of the spout serving as a nest entrance (May 11, 2025; photo by M. Wiśniewski). 7 Fig. 6. Interior of the Japanese-style teapot occupied by the colony of C. nicobarensis; the queen is partially visible in the upper left corner (May 11, 2025; photo by M. Wiśniewski). Fig. 7. Interior of the Japanese-style teapot serving as the main (queenright) nest of the C. nicobarensis colony (October 24, 2025; photo by M. Wiśniewski). 8 DISCUSSION The nesting of C. nicobarensis in empty ceramic vessels described here obviously bore no resemblance to these ants' usual manner of nesting (a system of chambers and galleries in wood carved out by the ants themselves). Despite this, in these highly atypical nests, the queen laid eggs, and the offspring developed fully. It should be emphasized that the ants successively settled in the two teapots by their own choice, abandoning their previous nest locus in a pot filled with soil, and the colony has been functioning in a human dwelling, i.e. a completely artificial habitat, for a long time. This proves the extraordinary ecological plasticity and adaptability of the species. At the same time, this story prompts us to look at the issue from a different perspective: the potential threats posed by the spreading vogue for home ant keeping and the virtually unrestricted exotic ant trade conducted by online stores – even if this trade excludes species already recognised as invasive. Unfortunately, apart from shops operating legally (i.e. registered), a significant part of this trade takes place in the grey zone, beyond any control. After all, whether a species can be invasive once it has been introduced somewhere outside its natural range is only revealed after the fact. Nowadays, it is possible to obtain ants (as well as other invertebrates) from virtually any part of the world. Let us note that these statements refer to ants in general rather than specifically to C. nicobarensis. The latter has never been found outside its natural range (apart from the obviously misleading data from North America (see above). However, several other ant species that have been widely sold (both legally and illegally) in Europe have been found successfully nesting outdoors outside Fig. 8. Interior of the Bulgarian-style teapot serving as the branch (queenless) nest of the C. nicobarensis colony (October 24, 2025; photo by M. Wiśniewski). 9 their natural ranges. At this point, it is worth noting that carpenter ants (Camponotus spp.) are generally considered pests of timber (like termites), which can cause damage to structural wood and furniture. In the reported case, the extraordinary survival skills of C. nicobarensis were revealed only after the colony had accidentally escaped from the formicarium in which it was kept. Such escapes of various exotic ant colonies kept at home from formicariums happen quite often; they are described by amateur ant keepers on their on-line forums. That is not so bad if it happens within an apartment, but it is not difficult to imagine a situation when a colony escapes outdoors (in the described case, the foragers appeared on the balcony, from where it was only a step to go completely outside). It is also not difficult to imagine the deliberate release of a home-kept colony into the environment by a bored ant-keeper. Ants are insects with a strong invasive potential. Many of them are among the most globally significant invasive species. They cause local decline and extinction of a variety of taxa of animals and plants alike, disturb ecosystem processes, decrease agricultural production, damage infrastructure and can be a health hazard for humans, being a major global problem (Bertelsmeier et al. 2014). The list of 100 most harmful invasive species of all organisms (including viruses), prepared by the International Union for Conservation of Nature, includes five ant species (38.5%) among the 13 insect species listed there (Lowe et al. 2000). The importance of the problem is evidenced by the 2283 (until 2012) matching items in the popular ant bibliography 'Formis' indicated after entering 'ant invasion' as a keyword (1677 items after 2000). Invasions of alien ants, which are harmful both to the local nature and humans, have affected practically all continents and climate zones. For example, in Central Europe, such a species is the invasive garden ant Lasius neglectus van Loon, Boomsma et Andrásfalvy. It comes from Asia Minor, from where it was introduced to Europe along with potted plants in the 1970s, where it spread rapidly between cities in the same way, gaining a reputation of being one of the most problematic ant species (van Loon et al. 1990, Nagy et al. 2009, Seifert 2000, Cremer et al. 2008, Ugelvig et al. 2008). Incomparably more extensive is the spread of the highly invasive Argentine ant [Linepithema humile (Mayr)] originating from the tropics of South America. This is a species, as it turned out, with extraordinary adaptive abilities which, due to human activities such as transport and trade, has invaded other continents (North America, Africa, Australia, Pacific islands, and even Europe) where it has become well established in regions with a suitable climate (Angulo et al. 2024). The global plant and animal trade poses a serious challenge to nature conservation, as the artificial introduction of alien species is one of the leading causes of biological invasions. Periods of increased invasions have corresponded to two major waves of globalization (Bertelsmeier et al. 2017, Bonnamour et al. 2018). Introduction events, combined with rising temperatures due to climate change, provide a unique opportunity for many species, especially insects, to colonise new areas that were previously unsuitable for them due to unfavourable environmental conditions (Goodisman 2023, Mwebaze et al. 2023). Introductions of alien insects are a serious concern because they threaten the balance of natural ecosystems; possible ant invasions deserve special attention because alien ants can dominate native local communities (Bertelsmeier 2023). The growing interest in ants as pets increases this threat, as the most popular species among ant keepers are exotic species. This situation is exacerbated by the fact that many illegal sellers see this as a source of easy income, especially since there is no regulation of such online trade. Currently, more than 500 species of ants are traded online worldwide (Gippet & Bertelsmeier 2021). According to our cursory analysis of official store offers, private