Plagiolepis pygmaea (Latreille, 1798)

Khalife, Adam & Peeters, Christian, 2021, Food storage and morphological divergence between worker and soldier castes in a subterranean myrmicine ant, Carebara perpusilla, Journal of Natural History 54 (47 - 48), pp. 3131-3148 : 3140-3141

Interactions with Plagiolepis pygmaea

Carebara perpusilla workers moved soil pellets and corpses to build thick barricades inside their tunnels that separated them from the Plagiolepis pygmaea colony ( Figure S3 ). Some non-replete soldiers stayed close to these barricades. Therefore, interactions between P. pygmaea and C. perpusilla workers happened exclusively outside the nest and were most aggressive next to common food resources ( Figure 6 ). Three P. pygmaea foragers tried to bite the legs of a C. perpusilla worker. One P. pygmaea was spotted carrying an immobile C. perpusilla worker back to its nest, but dropped it when picked up with forceps, and the immobile worker started moving again and walked back to its nest. Multiple dead C. perpusilla workers and soldiers were found inside P. pygmaea chambers. Surprisingly, several P. pygmaea scouts walked a few millimetres away from a freshly buried mealworm without stopping.

One day, two C. perpusilla workers chased away a P. pygmaea scout that was drinking haemolymph from a dead mealworm (five C. perpusilla were already on it). But that scout came back two minutes later with five other workers, one seen with the gaster raised. After another two minutes, the number of P. pygmaea workers became ten and one bent the gaster down (possibly to spray formic acid, not seen). Two minutes later, twenty-two P. pygmaea were facing the five C. perpusilla workers. One C. perpusilla opened its mandibles and made one P. pygmaea walk away, but the Carebara were outnumbered. After six more minutes, forty-five P. pygmaea were on the mealworm. Three C. perpusilla remained: two remained immobile (possibly sprayed with acid) and one was bitten. In another episode, thirteen C. perpusilla were on a mealworm; a single P. pygmaea scout avoided getting closer and ran away after interacting with the workers.

Figures

Figure 3. Comparison of C. perpusilla castes showing worker (top-left), soldier (top-right) and queen (bottom-left). For the queen, a replete gaster was added as an inset (bottom-right, same scale).

Figure 6. Competitive interaction between one C. perpusilla (black arrow) and two P. pygmaea (antennas pointing forwards, red arrow and asterisk). Other P. pygmaea feed on a dead mealworm.