Tandem Recruitment and Trail Laying in the Ponerine Ant Diacamma rugosum: Signal Analysis1

Abstract

AbstractDuring nest emigration, Diacamma rugosum scouts recruit female nestmates to the new nest site by tandem running. ♂♂, brood and prey objects are carried.The tandem leaders stimulate their nestmates to follow them by pushing or, more rarely, pulling them with the mandibles.The signals releasing the following behaviour are mainly chemical. Only 15–30% of motivated followers react positively to an odourless paper or wax dummy. The ♀♀ follow cut‐off thoraces, legs and gasters plugged at the end or without hind gut and sting apparatus, just as well as a leading ant. The ants even follow a dummy consisting of body parts if they are not in direct mechanical contact with it. The leading effect of the body surface is not reduced by intensive cleaning with water or by extraction in solvents of different polarity. Only maceration in potash lye eliminates the leading effectiveness of the cuticula. None of the secretions of the tested abdominal glands release following behavior. Only the hind gut fluid possesses leading signal qualities. No distribution of faeces over the bodies of the leading ants can be observed before or during tandem running. The faecal pheromone responsible for this leading effect does not seep into the superficial layer of a leader dummy made from bee wax but it can be washed off with water. These results show that the actual signal releasing tandem following is an unspecific odour substance of the cuticula surface. The presence of the hind gut fluid is not necessary for the tandem following response. It may be an additional signal. During nest emigration the hind gut fluid is scattered patchily in the form of small droplets by the nest finders on their way to the new nest. No increased deposition of faecal droplets could be observed on the way to repeatedly visited rich food sources.The hind gut fluid serves as a long lasting trail substance and has an exclusively orienting effect. The secretions of the other abdominal glands are not trail pheromones. The nest entrance is marked colony‐specifically.