ASIAN MYRMECOLOGY Volume 10, e010011, 2018 ISSN 1985-1944 | eISSN: 2462-2362 © Herbert Zettel, Alice Laciny, Weeyawat Jaitrong, DOI: 10.20362/am.010011 Syaukani Syaukani, Alexey Kopchinskiy and Irina S. Druzhinina Evidence of predation in two species of the Colobopsis cylindrica group (Hymenoptera: Formicidae: Camponotini) Herbert Zettel1, Alice Laciny1, 5*, Weeyawat Jaitrong2, Syaukani Syaukani3, Alexey Kopchinskiy4 and Irina S. Druzhinina4 12nd Zoological Department, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria. 2Thailand Natural History Museum, National Science Museum, Technopolis, Khlong 5, Khlong Luang, Pathum Thani, 12120 Thailand. 3Biology Department, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam 23111, Banda Aceh, Indonesia. 4Research Area Biochemical Technology, Institute of Chemical, Environmental and Biological Engineering, TU Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria. 5Department of Theoretical Biology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria. *Corresponding author: [email protected] ABSTRACT. The complex ecology and nutrition of “exploding” ants of the Colobopsis cylindrica group (COCY) is still poorly understood. Hitherto, this group of ants was thought to feed mainly on phylloplane biofilms with only scarce observations of carnivorous behaviour. This study focusses on observations and behavioural experiments conducted on Colobopsis badia and Colobopsis leonardi, two species native to Thailand. In experiments with C. leonardi, we investigated recognition and acceptance of diverse arthropod prey, as well as its mode of transport into the nest. In addition, preliminary data on C. badia were collected. We present the first recorded instances of predation for these species and discuss our findings in the light of previously published hypotheses on COCY nutrition and behaviour. Keywords: carnivory, exploding ants, nutrition, Southeast Asia, Thailand INTRODUCTION cies points to plant exudates or microbes from the phylloplane biofilm as their primary source The “exploding” ants of the Colobopsis cylin- of nitrogen (Davidson et al. 2016). During ex- drica group (COCY) are particularly known for tensive observations at the Kuala Belalong Field their self-sacrificing defensive behaviour (auto- Studies Centre (KBFSC) in Brunei Darussalam, thysis), but have also been the object of several workers have never been observed to hunt or ecological studies (e.g., Cook 2008, Davidson et feed on animal carcasses. However, fragments al. 2007, 2009, 2016; Laciny et al. 2018). How- of unidentified arthropod exoskeletons have ever, the nutrition of imagines and larvae still been found within the buccal pellets of COCY remains an unanswered question. Isotopic evi- workers (Davidson et al. 2016). dence from six examined Bornean COCY spe- 2 Herbert Zettel, Alice Laciny, Weeyawat Jaitrong, Syaukani Syaukani, Alexey Kopchinskiy & Irina S. Druzhinina In feeding experiments carried out at niques of transport: Yamamoto et al. (2009) com- the same location between 2015 and 2017, two pared different modes of prey transport between COCY species, Colobopsis explodens, Laciny & arboreal and ground-nesting ants of Southeast Zettel 2018, and an undescribed species related Asia. Among the studied species was “Colobop- to Colobopsis leonardi Emery, 1889, accepted sis sp. nr. leonardi” – presumably a member of various offered food items (fish, fruit, biscuit the COCY group. The study found that this spe- crumbs), but only transported small dead insects cies, as well as the vast majority of other arboreal and arthropod body parts. In experimental set- species, divided large prey into smaller pieces tings, no instance of feeding on spores or hyphae that were then carried into the nest by individual of filamentous fungi (such as molds) was ob- workers without cooperation. In contrast, ground- served, but a suspension of yeasts was accepted nesting ants tended towards cooperative retrieval (M. Rahimi, unpublished data). However, on of prey. Furthermore, the mode of prey transport their foraging grounds, workers were frequently by individual ants is influenced by the size and seen plucking mosses, lichens and fungi from weight of the transported item: Small items are the surface of bark or leaves (“grazing”), which preferentially lifted while the ant is facing for- has previously been hypothesized to contribute to ward; heavy or large items are dragged while the their nutrition (Laciny et al. 2018, compare Da- ant walks backwards (Sudd 1960; see Czaczkes vidson et al. 2007, 2016). & Ratnieks 2013 for a review). We aimed to as- It is well known that ant larvae require sess whether these correlations are also applica- protein-rich nutrition during their development ble to the examined COCY species. (e.g., Hölldobler & Wilson 1990, Dussutour Finally, we attempted to investigate & Simpson 2009). How these needs are met in the use of different nest entrances for bringing larvae of the COCY group is hitherto unknown. prey into the nest. COCY ants are polydomous However, several reports of arthropod carcasses with large colonies containing many thousands being accepted and transported into the nest in- of individuals (Federle et al. 1998, Laciny et al. dicate that COCY larvae may be fed with animal 2017, Laciny et al. 2018). Especially members of protein: Hashimoto et al. (1997) reported that the C. saundersi complex willingly and rapidly “Camponotus saundersi Emery, 1889” (species colonize artificial nests and use them to rear their identity unconfirmed) accepted freshly killed brood (Davidson et al. 2009, Laciny et al. 2017, mosquitoes in an experimental setting on Borneo, Laciny et al. 2018). This suggests a form of nest and Yamamoto et al. (2009) reported that Colob- partitioning also corroborated by the presence of opsis sp. nr. leonardi in Indonesia fed on offered carton partitions in detached nest fragments (A. mealworms. Another author (W. Jaitrong, unpub- Kopchinskiy, I. Druzhinina, unpublished data). lished data) has observed that Colobopsis leon- This may result in the allocation of protein-rich ardi, a common COCY species in Thailand, car- animal prey to specific parts of the nest. ries insect prey. Moreover, a mermithid infection Molecular and morphological analyses of adult ants of Colobopsis sp. nrSA in Brunei (Cook 2008, Laciny et al. 2018, Zettel et al. un- suggests that earthworms or insects were fed to published data) have identified at least three dis- the ants’ larvae: Mermithid nematodes are known tinct subclades native to Southeast Asia: The C. to be transmitted when intermediate hosts (oligo- saundersi complex, the C. leonardi complex, and chaetes or aquatic insects) containing the nema- the eponymous C. cylindrica complex. In this pa- todes’ infective larval stages are fed to the host per, we describe observations and standardized ants’ larvae (Kaiser 1986, Poinar 2012, Laciny et experiments on selected colonies of two COCY al. 2017). These findings suggest that contrary to species, Colobopsis leonardi from the C. leon- previous hypotheses, these ants’ nutrition is not ardi complex and Colobopsis badia from the C. solely based on plants and microorganisms of the saundersi complex, in the Khao Chong Botanical phylloplane biofilm but also includes some form Garden in southern Thailand. of animal predation. We aimed to assess prey recognition and When animal prey is carried into the acceptance by offering various living and dead nest, ants are known to employ different tech- arthropods and oligochaetes. In addition, we re- Predation in the Colobopsis cylindrica group 3 corded the modes of transport employed by ants trances termed according to approximate cardinal dealing with prey items of different species and direction). Entrance W consisted of a single hole, sizes, as well as differential utilization of avail- entrances E and N of two holes in close vicinity able nest entrances. We present the first evidence (ca. 3 and 7 cm apart, respectively); the round en- of insect predation and acceptance of animal prey trance holes had a diameter of ca 3–5 mm. A trail for the studied species and interpret our results between entrances E and W was used by forag- within the framework of previous studies on the ing workers continuously and in high frequency enigmatic nutrition of the COCY group. in both directions, constituting the majority of the observed worker activity. MATERIAL AND METHODS 2.2. Prey recognition and entrance selection First, various arthropods, arthropod body parts, 1. Specimens, depositories and identification and earthworms were offered at the trail of C. leonardi (Table 1). During these experiments, it Studies were carried out on June 6–7, 2016 in the was observed that the entrance the prey was trans- Khao Chong Botanical Garden, Trang Province, ported to was strongly biased towards entrance E. southern Thailand. Both colonies were found For the following experiments concerning the se- at the sides of a trail leading from a parking lection of entrances, the branch section between area to the Ton Pliw Waterfall (N 07°32’34’’ E entrances E and W was divided into five sections 99°47’33”, ca. 150 m a.s.l.). of ca. 75 cm length (1–5, numbering starting at Colobopsis leonardi and Colobopsis ba- entrance E). Single prey items were offered by dia were identified by comparison with the types alternating between sections, starting at one and deposited in the Museo Civico di Storia Naturale ending at five. Four species of prey (Coptotermes Giacomo