A Formica Slave‐Maker Raiding the Nest of a Myrmicine Ant

Slave-making Formica of the sanguinea group normally raid the nests of Formica of the fusca, pallidefulva or neogagates groups to obtain pupae to be reared into slavery. Occasionally, F. sanguinea group species have been seen to raid other formicine genera, especially Lasius, and Wheeler (1905, Bull. Amer. Mus. Nat. Hist. 21: 11) even recorded a raid on a nest of Myrmica (subfamily Myrmicinae) species that he watched in Connecticut. Raids by Formica on myrmicines apparently are rare occurrences, so the circumstances of such a raid are worth reporting. On August 22, 1958, at Brown County State Park, Indiana, I witnessed a raid by Formica subintegra Emery on a nest of the much smaller myrmicine ant Aphaenogaster rudis Emery. The nest entrances of the raiders and the victims were simple holes situated only about one meter apart in the bare clay soil of a hilltop campground, shaded by hickories and a few oaks. The raid was firs noticed at about 3 P. M., about 3 hours after a heavy rain had ceased. The sky was partly cloudy, and the air temperature stood t about 70OF. Most of the visible activity occurred in and around the entrance to the A. rudis nest. Six dead or badly maimed rudis workers lay near the entrance, accompanied by one crippled F. subintegra worker. One subintegra worker grappled with a rudis worker and put it out of action while I watched. At irregular intervals, subintegra workers emerged, most of them carrying a pupa or a dead or struggling worker of A. rudis, with which they returned directly to their own nest and entered there. Two subintegra workers carried folded-up workers of their own species; when disturbed, these workrs dropped their burdens, which proved to be active and pparently unhurt.