L'Impregnation Dans L'Ontogenese Des Comportements De Soins Aux Cocons Chez La Jeune Fourmi Rousse (Formica Polyctena Forst.)

Abstract

Young worker ants of the species Formica polyctena separated from the mother-colony on the day of hatching and reared in groups of 250 to 300 individuals will accept and care for the cocoons of a different species, even of a different genus (Formica sanguinea, F. pratensis, Camponotus vagus, and Lasius niger). If such a group of young workers has been in contact, during the first fifteen days of life, with cocoons of one or another of these species (and in the absence of cocoons of their own species) only cocoons of this same species are subsequently accepted and tended. Cocoons of their own species are not recognised as such but treated as food. Worker F. polyctena which have matured in the presence of cocoons of their own species devour those belonging to strange species. When cocoons are totally absent from their early environment the workers turn out to be incapable of tending the cocoon of any species, including their own kind. It thus appears that the first fifteen days of life constitutes a critical or sensitive period during which the stimulation received by young worker from the cocoons has a powerful influence on the behaviour which it will later manifest as an adult. This stimulation appears, indeed, to be an indispensible element in ontogenesis of the behaviour of caring for the cocoons. In the majority of the experimental colonies the familiar cocoons are still recognised after a six months period of hibernation, in the absence of all cocoons. It seems that the characteristics of this phenomenon, and those of a sensitive period and memorization in particular, are essentially those of Imprinting as described in various Vertebrates. An unusual aspect of the phenomenon however, which is related to the social structure existing among ants, is provided by the fact that the efficiency of the imprinting is increased by the presence of a queen amidst the cocoons during the sensitive period.