Defensive effect of soldier-specific secretion by Reticulitermes speratus (Isoptera: Rhinotermitidae) on the facultative termitophagous ponerine ant Brachyponera chinensis (Hymenoptera: Ponerinae)

Abstract

Soldiers of the Japanese subterranean termite Reticulitermes speratus Kolbe possess the caste-specific terpenoid hydrocarbon β-selinene in the frontal gland. They secrete the compound as an alarm pheromone when facing danger. Furthermore, while dispersing the nestmate workers it simultaneously recruits the nestmate soldiers and enhances their aggression level. This study aims to confirm that the alarm pheromone might have defensive effects against facultative termite-hunting (termitophagous) ants, such as the Asian needle ant Brachyponera chinensis Emery. According to our behavioral bioassay, which provided fresh termite bodies, the ponerine ants used in the study immediately fed on the termite workers but avoided feeding on the soldiers. However, they avoided feeding on the workers when presented with the soldiers. Furthermore, extracted chemicals from the termite soldiers showed similar effects on the foraging activity of the ponerine ants, while those from the workers had no such effect. Soldier chemicals also clearly repelled the ponerine ants when they were treated at the entrance of a glass tube in which the worker bodies had been placed. It is most likely, therefore, that the termite soldier secretions serve as a chemical defense against the termitophagous ponerine ants.