The Effect of Early Experience on the Development of “Aggressive” Behaviour in Formica lugubris Zett. (Hymenoptera: Formicidae) 1

and Summary The possible rôle of early experience in the development of aggression in Formica lugubris Zett. was examined by setting up artificial colonies containing young workers hatched on the same day. Group 1 consisted of young workers hatched in the presence of homospecific adults, and so having “normal” experience. Group 2 young workers were reared from hatching with Formica rufa L. adults, and so had “altered” experience. Group 3 had young workers drawn from cocoons and reared in isolation from adults. Intra‐ and interspecific aggressive behaviour of the young workers in the three categories were analysed and quantified 16 and 30 days after hatching, after staging fights with F. lugubris and F. rufa . In group 1 no conspecific aggression was evident, but attacks were almost always recorded in heterospecific encounters. In group 2 there was no tolerance of homospecifics, initial contact frequently being followed by immediate over attack with all elements of aggressive behaviour. The reverse applied for F. lugubris with “altered” learning and F. rufa workers, there was mutual recognition and acceptance, as they were ants of the same colony. The young workers reared in isolation (group 3) fought in 60 % of homospecific encounters on the 16th and 40% on the 30th day; disturbance of conspecific recognition was clear. Nevertheless combat occurred in almost all heterospecific encounters. This work demonstrates that differences in early experience may influence the amount and direction of aggression in F. lugubris ant‐workers at 16 and 30 days of age. This may explain the existence of slave‐workers in natural dulotic societies. Zusammenfassung Der Einfluß früher Erfahrungen auf die Entwicklung der Aggression bei der Ameise Formica lugubris wurde in künstlichen Kolonien an Arbeiterinnen geprüft, die am jeweiligen Tag geschlüpft waren, und zwar in Gruppe 1 unter Artgenossen, in Gruppe 2 unter Erwachsenen von Formica rufa ; Arbeiterinnen der Gruppe 3 waren aus Kokons geholt und handaufgezogen. Inner‐ und zwischenartliches Angriffsverhalten wurden am 16. und 30. Tag nach dem Schlupf analysiert. In Gruppe 1 gab es keine deutliche Aggression zwischen Artgenossen, wohl aber beim Zusammentreffen mit F. rufa . — In Gruppe 2 gab es bei den ersten Kontakten mit Artgenossen häufig sofort Angriffe und alle Elemente aggressiven Verhaltens; hingegen waren die aus derselben Kolonie stammenden F. lugubris und F. rufa friedlich miteinander. — Isoliert aufgezogene Arbeiterinnen kämpften am 16. Tag in 60%, am 30. Tag in 40% der Begegnungen mit Artgenossen, aber auch in fast allen Begegnungen mit Artfremden. Frühe Erfahrung hat also einen Einfluß auf das spätere Aggressions‐verhalten. Das dürfte bei Sklavenhalter‐Ameisen eine Rolle spielen.