Der Hochzeitsschwarm der Rossameise Camponotus herculeanus L. (Hym. formicidae)

1. In the area of Würzburg (Westgermany) Camponotus herculeanus swarms from mid-may till the middle of June. Each nest containing young sexually mature ants produces from 2 up to 5 swarms. 2. A characteristic "sun bathing" of both sexes precedes the mating flight. 3. Intensity and timing of swarming depend on temperature. Sun bathing behavior as well as onset and performance of swarming show a diurnal rhythmicity. The mating flight starts between 5 and 7 PM. 4. The males begin swarming, the females swarm starts like an avalanche just when the bulk of the males takes off at the level of the flight hole. The females climb the branches of the tree and then fligh off. 5. The swarming of the bulk of both sexes is synchronized by odor. The males release during highest swarming activity a strongly smelling secretion from their mandibular glands which stimulates the females to take off, too. The alarming efficiency of the secretion increases the closer the natural time for the take off approaches - both in regard to season and daytime. 6. The females are only stimulated to take off by the odor not attracted. 7. Females of Camponotus herculeanus are not only stimulated by the mandibular secretion of the males of their own species but also by that of males of C. ligniperda. 8. The biological significance of the coordinated mass flight is discussed.