Olfactory Learning Phenomena and Cocoon Nursing Behaviour in the AntFormica RufaL.

Abstract

Further tests have been carried out to confirm the existence of learning phenomena in parental care (cocoon nursing) by the ant Formica rufa L. It has already been shown by us (1977) that worker-ants of this species recognize and look after the homo- or heterospecific cocoons which they were familiar with and had experienced during the first 15 days after hatching. It has been possible, through qualitative as well as quantitative evaluations, to ascertain that stimuli induced by cocoons are essential in the ontogenesis of recognition processes hence of nursing behaviour. Thus, F. rufa workers, reared in the absence of any cocoon, from the time of hatching throughout the whole sensitive period, when subsequently given a choice between homo- and heterospecific cocoons, showed neither recognition nor nursing behaviour. Furthermore, chemical stimuli from the cocoons seem to be of paramount importance in eliciting adoption behaviour. Cocoons of Formica lugubris Zett. impregnated with substances, probably pheromones, derived from intact F. rufa cocoons and contained in the lipid fraction (ether extract), proved more attractive to and were tended for a long period by young F. rufa workers with “normal” learning, which usually consider non-impregnated heterospecific cocoons only as food. This kind of learning, which may depend from olfaction, might explain, at least in certain cases, the keeping of slaves and the nursing behaviour of slave ants in dulotic ant societies.