PROXIMATE FACTORS OF SINGLE FEMALE FOUNDING IN THE PAPER WASP POLISTES-GALLICUS L

In laboratory studies, we investigated the factors which caused the fa ilure of joining associations amongst foundresses of the haplometrotic paper wasp species Polistes gallicus. All the associations were succe ssful when two foundresses were brought together immediately after the diapause. However, the success rate dropped to 59% when females were isolated for 8 days from the end of the diapause to the time of the '' encounter'' experiments. The wasps were allowed to develop two-foundre ss colonies for 10 days. Then we exchanged the foundresses in order to bring two unacquainted females together. When encounters took place o n nests containing a well developed larval brood, the success rate was only 45%. However if there was no nest or a small nest without larvae , 90% of the encounters were successful. We therefore concluded that t he failure of joining associations cannot be entirely explained by the hypothesis that there is a sensitive period for developing associatio ns to build nests. Isolation certainly perturbed the capacity to estab lish stable social relationships. On the other hand, the level of aggr ession between unacquainted females increased if the brood was develop ed, regardless of the origin of the nest. Familiarisation between fema les allows cofoundresses to cohabit on a developing nest, despite the increase in aggression. Nevertheless, comparison with others species s uggests that the difference between the haplometrotic and pleometrotic species is less due to the specific level of aggression itself than t o the way foundresses cope with this aggression.