Defensive behaviour and biological activities of the abdominal secretion in the ant Crematogaster scutellaris (Hymenoptera: Myrmicinae)

*[Using bioassays, the defensive behavior of Crematogaster scutellaris and the biological activities of its abdominal secretion were investigated. Beside classical aggressive behaviors such as gripping, C. scutellaris workers performed frequent characteristic gaster flexions during interspecific encounters, sometimes attempting to apply their abdominal secretion topically on the enemy. The toxicity of the venom of C. scutellaris to other ants greatly differed among the species tested, some being killed after the topical application of only 3 droplets, while others were quite resistant to a dose of 90 droplets. All ant species tested were strongly and immediately repelled by a contact between their antennae or mouthparts with the venom of C. scutellaris. Abdominal secretion was never used during intraspecific interference and workers were resistant to a topical application of the venom of their own species. Intraspecific repellency was significant but moderate compared to interspecific repellency. Workers of C. scutellaris were never seen using their venom during prey capture. In conclusion, the main biological activity of the abdominal secretion of C. scutellaris seems to be its repellency to other ant species. This is supported by field experiments showing that Pheidole pallidula foragers were efficiently repelled at coexploited baits, allowing the monopolization of most prey by C. scutellaris.]