title: Factors affecting the regurgitation behaviour of the ant Lasius flavus (Formicidae) to the guest beetle Claviger testaceus (Pselaphidae).
abstract: Workers of regularly fed Lasius flavus ants regurgitate ingluvial food on the mouthparts of the guest beetle Claviger testaceus in response to the licking of particular secretions of the myrmecophile. These regurgitations typically occur with the workers' mandibles joined and antennae immobile, in a U-shaped position, even if the colony's diet consists exclusively of insect meat or of a low-concentrated (2.5%) sugar solution. In addition, when the dietary sugar concentration exceeds 5%, workers may disgorge spontaneously, with mandibles spread apart and antennae folded backwards, the funiculi divergent. Replete (i.e., over-fed) ants present the same spontaneous behaviour. The ratio of the number of régurgitations to the number of licking sessions on the Claviger's mouthparts is the highest in workers with a moderately filled crop. Such workers therefore provide the beetle with the greatest number of regurgitations. Repletes and, of course, starving workers provide less regurgitations to the beetle. The quantity of liquid food regurgitated on the Claviger also appears to be maximum in workers with a moderately filled crop. The workers' regurgitation rate is higher in laboratory colonies collected from the field and kept for some months than in colonies only recently collected. This effect may be linked to the overall age of the worker populations of the laboratory nests. The presence of a queen does not affect the workers' regurgitation rate. However, her presence does increase the number of workers' licking sessions in mature colonies only recently settled in a laboratory and, consequently, increases to some extent the number of regurgitations on the beetle.
authors.affiliation: Laboratoire de Biologie Animale et Cellulaire, Faculté des Sciences, C.P. 160/11, Université Libre de Bruxelles, 50 av. F.D. Roosevelt, B-1050 Brussels, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Cammaerts