Zur Physiologie der Gast-Wirt-Beziehungen (myrmecophilie) bei Ameisen - II. Das Gastverhältnis des imaginalen Atemeles pubicollis Bris. (Col. Staphylinidae) zu Myrmica und Formica (Hym. Formicidae)

1. The myrmecophilic beetle Atemeles pubicollis Bris, changes its hosts obligatorily twice in its imaginal life: after emergence in July/August in the nest of the larvae-host Formica the beetle moves to Myrmica and returns to Formica after hibernation. Observations by Wasmann were confirmed in the field and in the laboratory. 2. 2-3 days of positive phototaxis and high activity take the beetles, 6-9 days after emergence, from the forest habitat of Formica to the open grassland nesting sites of Myrmica. 3. The beetles are attracted by the specific odour of Myrmica-nests; running clinotactically upwind they are guided to their host's nests. 4. The odour of the Myrmicine genera (Tetramorium, Solenopsis) attracts the guests also; however in an alternative choice situation Myrmica is always preferred. The odour of this species is even detected if it is offered in a mixture with the odour of other ants. 5. The beetles readiness to react to the Myrmica odour lasts only two weeks after leaving Formica. 6. During this time they are adopted by Myrmica: The guests do not actively intrude into their host's nest, but wait in front of the nest entrances until the ants carry them in. 7. This interest in adoption is induced in the ants by a secretion from the unicellular glands along the margins of the abdominal tergites. This secretion is only effective in host ants. In addition, pygidial gland secretion has a calming effect on the ants and another abdominal gland produces a repellent. 8. By using radioactive tracer (³²P) it could be shown that the beetles participate parasitically in the ants food exchange in the nests of Formica and in those of Myrmica.