oe JHR 78: 91-96 (2020) SSORNIE OEE ee erae doi: 10.3897/hr.78.54409 SHORT COMMUNICATION (ME Hymenoptera http://jhr.pensoft.net The Insertional Society of ymenoptersts. RESEARCH Observations of neotropical social wasps (Hymenoptera, Vespidae) preying on eggs and tadpoles of the frog Engystomops pustulosus (Amphibia, Leptodactylidae) Christopher K. Starr', Rakesh Bhukal’, Shane T. Ballah? | Caura Village, Trinidad & Tobago 2. School of Veterinary Medicine, University of the West Indies, Champs Fleurs, Trinidad & Tobago 3 National Herbarium of Trinidad & Tobago, University of the West Indies, St Augustine, Trinidad & Tobago Corresponding author: Christopher K. Starr (ckstarr@gmail.com) Academic editor: Michael Ohl | Received 18 May 2020 | Accepted 7 July 2020 | Published 31 August 2020 http://zoobank. org[AAC91 C1 0-6364-4BAA-829B-C9557C37C5CC Citation: Starr CK, Bhukal R, Ballah ST (2020) Observations of neotropical social wasps (Hymenoptera, Vespidae) preying on eggs and tadpoles of the frog Engystomops pustulosus (Amphibia, Leptodactylidae). Journal of Hymenoptera Research 78: 91-96. https://doi.org/10.3897/jhr.78.54409 Abstract In Trinidad, West Indies the social wasps Angiopolybia pallens and Polybia rejecta come to foam nests of the frog Engystomops pustulosus, where they prey on eggs and tadpoles. Frog offspring in early-stage foam nests appear to be almost immune to predation by the wasps, but they become more vulnerable as the nests age and lose definition. Keywords Angiopolybia pallens, Engystomops pustulosus, Polybia rejecta, predation, tingara frog Introduction Engystomops pustulosus (= Physalaemus pustulosus) (Cope) is a small, nondescript neo- tropical frog ranging from Mexico to northern South America (Rand 1983). In Trinidad, West Indies, it is one of six leptodactylids that lay their fertilized eggs into viscous foam nests (Murphy et al. 2018). Breeding takes place in very small, shallow, temporary pools. Copyright Christopher K. Starr et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 92 Christopher K. Starr et al. / Journal of Hymenoptera Research 78: 91-96 (2020) As the eggs are laid and fertilized, the female secretes a viscous, proteinaceous fluid, which the male beats into a foam with his hindlegs (Breeder 1946; Dalgetty and Kennedy 2010; Heyer and Rand 1977; Ryan 1985), rather like beating egg whites in the kitchen. This mass of white foam typically floats on the water surface, enveloping the eggs. The tadpoles may remain in the nest for up to five days before breaking through to the water below (Rand 1983). Foam nests of E. pustulosus can be distinguished from those of sympatric species in Trinidad by their placement, size and form (Murphy et al. 2018:113-123), so that they almost always can be identified with confidence even in the absence of adult or immature frogs. ‘They disintegrate over time, first becoming flatter and then losing their integrity. The speed of this process evidently varies accord- ing to external conditions. For example, heavy rain hastens the process (Ryan 1985). Adult £. pustulosus are taken by a number of predators (Rand 1983; Ryan 1985). Much less is known of the immature stages’ natural enemies. The foam nest has no discernible taste (pers. obs.), but it is presumed to provide substantial physical protec- tion to the eggs and the tadpoles as long as these latter remain inside it. Where the larger frog Agalychnis callidryas (Cope) is present, its tadpoles often eat E. pustulosus’s eges (Heyer and Muedeking 1976). Once out of the nest, the tadpoles are evidently vulnerable to a variety of predators, including tadpoles of the larger frog Leptodactylus pentadactylus (Laurenti) (Heyer and Muedeking 1976). The adults are often preyed upon by the bat Trachops cirrhosus (Spix) (Gomes and Reid 2015; Ryan 1985). Among Angiopolybia pallens (Lepeletier) is a swarm-founding social wasp that ranges from Panama south to Peru and central Brazil (Richards 1978:233). Accordingly, it is broad- ly sympatric with E. pustulosus in northern South America and part of Central Amer- ica. In Trinidad it is evidently the most abundant social wasp in forests (pers. obs.). Another swarm-founding wasp, Polybia rejecta (E), has a similarly broad distribution (Richards 1978:122), where it is similarly abundant in more open habitats. Both spe- cies forage on a broad variety of resources, including carrion (O’Donnell 1995), at which A. pallens is especially prevalent (Silveira et al. 2005; pers. obs.). P rejecta is known to prey on the eggs of A. callidryas (Warkentin 2000). Methods On 12 May 2018 we noticed several female A. pallens landing on E. pustulosus foam nests in the Arena Forest Reserve (10°33'N, 61°13'W) in central Trinidad. The habitat is mature secondary rain forest on rolling hills watered by many streams. The wasps appeared to be burrowing into the nests to a shallow depth. On 23 May we returned for further observations. All nests were in potholes in a degraded paved road. For our purposes, it is convenient to recognize three states of the completed nest. In stage 1, the nest is coherent and domed, commonly to 2-4 cm above the water, as when freshly produced (Fig. 1a). In stage 2, it remains coherent but is flattened throughout to no more than 1 cm (Fig. 1b), thereby in- creasing its surface/volume ratio. And in stage 3 it is distinctly losing its integrity (Fig. 1c). Social wasps preying on frog brood 93 Figure I. Stages in the disintegration of Engystomops pustulosus foam nests. a Stage 1; fresh, domed above the water b Stage 2; distinctly flatter, but still coherent ¢ Stage 3; very flat and losing coherence. 94 Christopher K. Starr et al. / Journal of Hymenoptera Research 78: 91—96 (2020) Table |. Pools in a degraded paved road in Trinidad and their complements of Engystomops pustulosus foam nests. See text for explanation of nest stages. One of the stage-2 nests in pool no. 1 was evidently an amalgamation of several original nests from different pairs of frogs. Pool no. Stage 1 Stage 2 Stage 3 Wasp visits? i 4 4 6 + Z 4 4 0 — S 0 1 0 - 4 1 0 0 - 2 1 1 2 + 6 1 0 0 + fy 0 3 0 + We made observations at seven pools varying in their composition of foam nests (Table 1). Pool no. 1 was exceptionally large with a surface area of roughly 1 m’. At this and several other sites along the road we found wasps landing on the nests. Most of the wasps were A. pallens, with only a very few P rejecta, so that all observations below are from the former species except where noted. Our attention was first draw to several A. pallens atop two stage-1 nests at a site with no other nests. Results Paring away three stage-1 nests from above, we found abundant dispersed eggs, with the outer 5 or 6 mm free of eggs. Exposed eggs were readily taken by wasps when we stepped away. Some wasps remained to eat the eggs on the spot, while others flew away with them. Our preliminary observations had been of wasps at a pool with only stage-1 nests. Where nests of different stages were found together, the wasps showed a distinct prefer- ence for stage-2 nests (Table 2). This preference is readily explained. Unlike in stage-1 nests, tadpoles were commonly visible just below the surface film of the much flatter nests. [hey tended to be made even more conspicuous by their movement. Stage-3 nests presumably had nothing to offer except foam. Wasps often fluttered their wings while walking over the nest surface, possibly as a way of avoiding becoming caught in the surface film. While A. pallens commonly bur- rowed to a depth of its entire head and part of its thorax (Fig. 2), P rejecta hardly pen- etrated below the surface in our observations. We observed several captures from stage-2 nests, but none by either species from a stage-1 nest except when we exposed eggs. A few times we saw P rejecta carrying away fragments of foam with no evident egg or tadpole. Lacey (1979) reported A. pallens collecting not only eggs and tadpoles but the foam itself from foam nests of Leptodactylus pentadactylus. However, in our observa- tions any collection of foam from E. pustulosus nests was at most a very occasional activ- ity, not at all like the large numbers of wasps that gather at fresh fruitfalls (pers. obs.) This suggests that nest foam is of only marginal nutritional value and was only taken by wasps that failed in the search for eggs or tadpoles. Social wasps preying on frog brood 95 Table 2. Wasp landings on Engystomops pustulosus foam nests in pool 1. Further explanation in text. Stage 1 Stage 2 Stage 3 Angiopolybia pallens 3 50 0 Polybia rejecta 5 15 0 Figure 2. Angiopolybia pallens burrowing into an Engystomops pustulosus foam nest. Discussion While characterizing social wasps as “opportunistic, generalist prey foragers”, Raveret- Richter (2000) notes that individuals may return repeatedly to sites of earlier hunting success, making them facultative specialists. E. pustulosus’s foam nests are large, very conspicuous (white against the mainly dark forest floor) and stationary. Accordingly, any wasp that has learned to access the abundant eggs and/or tadpoles has good reason to specialize on any nest that she encounters. Acknowledgements Thanks to R.L. Jeanne, J.C. Murphy, and S. O’Donnell for comment on of our obser- vations, J. Spiers for graphic assistance, and the journal’s reviewers (R. Auguste, J.M. Carpenter and C.E. Sarmiento) for suggesting improvements. 96 Christopher K. Starr et al. / Journal of Hymenoptera Research 78: 91—96 (2020) References Breeder CM (1946) Amphibians and reptiles of the Rio Chucunaque drainage, Darién, Pan- ama, with notes on their life histories and habits. Bulletin of the American Museum of Natural History 86: 375-436. Dalgetty L, Kennedy MW (2010) Building a home from foam — tingara frog foam nest ar- chitecture and three-phase construction process. Biology Letters 6: 293-296. https://doi. org/10.1098/rsbl.2009.0934 Gomes GA, Reid FA (2015) Bats of Trinidad and Tobago. Trinibats (Port of Spain): 1-286. Heyer WR, Rand AS (1977) Foam nest construction in the leptodactylid frogs Leptodactylus pentadactylus and Physalaemus pustulosus (Amphibia, Anura, Leptodactylidae). Journal of Herpetology 11: 225-228. https://doi.org/10.2307/1563148 Heyer WR, Muedeking MH (1976) Notes on tadpoles as prey for naiads and turtles. Journal of the Washington Academy of Science 66: 235-239. Lacey LA (1979) Predac4o em girinos por uma vespa e outras associagées de insetos com ninhos de duas espécies de ras na Amazénia. Acta Amazonica 9: 755-762. https://doi. org/10.1590/1809-43921979094755 Murphy JC, Downie JR, Smith JM, Livingstone SM, Mohammed RS, Lehtinen RM, Eyre M, Sewlal JN, Noriega N, Casper GS, Anton T, Rutherford MG, Braswell A, Jowers MJ (2018) A field guide to the amphibians & reptiles of Trinidad & Tobago. Trinidad & To- bago Field Naturalists’ Club (Port of Spain): 1-336. O’Donnell S (1995) Necrophagy by neotropical swarm-founding wasps (Hymenoptera: Vespi- dae: Epiponini). Biotropica 27: 133-136. https://doi.org/10.2307/2388911 Rand AS (1983) Physalaemus pustulosus (rana, sapito tingara, foam toad, muddle-puddle frog). In: Janzen DH (Ed.) Costa Rican natural history. University of Chicago Press (Chicago): 412-415. Raveret-Richter M (2000) Social wasp (Hymenoptera: Vespidae) foraging. Annual Review of Entomology 45: 121-150. https://doi.org/10.1146/annurev.ento.45.1.121 Richards OW (1978) The social sasps of the Americas, excluding the Vespinae. British Museum (Natural History) (London): 1-580. Ryan MJ (1985) The Tingara Frog. University of Chicago Press (Chicago): 1-246. Silveira OT, Esposito, MC, Santos JN dos, Gemaque FE (2005) Social wasps and bees captured in carrion traps in a rainforest in Brazil. Entomological Science (Tokyo) 8: 33-39. https:// doi.org/10.1111/j.1479-8298.2005.00098.x Warkentin KM (2000) Wasp predation and wasp-induced hatching of red-eyed treefrog eggs. Animal Behaviour 60: 503-510. https://doi.org/10.1006/anbe.2000.1508