Social Organization in the Guest-ant Formicoxenus provancheri

The results of an investigation on the division of labour in the guest-ant Formicoxenus provancheri, conducted by observing colonies containing individually marked adults, are presented. Five colories of Formicoxenus were installed in the laboratory with their hosts, Myrmica incompleta, in order to document, over 10 d, the location of individuals as well as individual and interactive types of behaviour. The results show that each colony of Formicoxenus consists of three groups: a group of nurses who remain in the Formicoxenus nest (some 21% of the colony's members); a group of scouts who spend most of their time in the external area (18%) and a very large group of individuals specialized in licking (‘shampooing’) the host to obtain regurgitations (61%), who essentially remain in the Myrmica nest. Division of labour in Formicoxenus appears to be a special adaptation to the xenobiotic way of life. The apparent link between social structure and the probability of profiting from trophallactic exchanges with the host species could lead to interesting predictions on the division of labour in other guest-ants.     

The sensitivity and responsiveness of ants to their cocoons in relation to age and methods of measurement

Groups of 200 young Formica polyctena ants reared from birth in the presence of cocoons for two weeks developed an effective cocoon-nursing behaviour. In the course of varying the age of the ants when first exposed to the cocoons, one test gave a negative result, whereas another test suggested that the first week of exposure to the cocoons is decisive and the second week ineffective. When the development of the ants' sensitivity to cocoons as a function of age was studied in groups of two young workers, the sensitivity was found to be pronounced and unchanging if the ants had been exposed from birth to cocoons. If the ants were not exposed to cocoons before the test, their sensitivity varied markedly with age, reaching a maximum at 48 h. These results raise the question whether divergent views on the issue of sensitive periods does not merely reflect differences in experimental procedure.