Bumblebee inquilinism in Bombus�(Fernaldaepsithyrus) sylvestris (Hymenoptera, Apidae): behavioural and chemical analyses of host-parasite interactions

Abstract

-The bumblebee Bombus sylvestris is an obligate social inquiline of B. pratorum and nestinvading females are known to integrate themselves into host colonies, usually without any aggression. We investigated whether cuticular compounds could be involved in discrimination processes in common bumblebees, and whether they play a role in the social integration of inquilines in host nests. We tested nestmate recognition in B. terrestris workers, and analysed cuticular chemical profiles of hairs taken from allocolonial individuals. Bumblebees belonging to the same colony shared a common odour. Then, we investigated how B. sylvestris females integrated into colonies of natural and non-natural hosts, B. pratorum and B. terrestris, respectively. Inquiline females apparently succeeded in entering a host colony by expressing non-aggressive behaviours and had no chemical signature; subsequently, acquisition of a chemical signature similar to the host colony might facilitate their integration into the host nest.Bombus sylvestris / inquilinism / discrimination process / chemical signature / non-aggressive strategy

Reduced cephalic labial glands in the male bumblebees of the subgenusRhodobombusDalla Torre (Hymenoptera: Apidae:BombusLatreille)

“…Hydrocarbons are implicated in intraspecifi c communication, including premating behaviour but they are usually acting at very short distance or by contact (Ginzel et al 2003;Dronnet et al 2005).…”

A larval hunger signal in the bumblebee Bombus terrestris

“…Clear differences in feeding frequencies, were observed, suggesting that worker bumblebees can recognise hungry larvae by their cuticular chemicals and that these chemicals can act as a hunger signal. These cuticular chemicals are probably mainly hydrocarbons, because a) n-pentane is a solvent for lipid mixtures rich in hydrocarbons (Howard, 1993); and b) hydrocarbons are known to be widely involved in insect communication, for example as cues for nest mate recognition, sex discrimination, and caste recognition (Howard, 1993;Winston, 1992) but also in host-parasite interactions (Lenoir et al, 2001;Dronnet et al, 2005). These are all long-term recognition functions and the synthesis and spreading of these hydrocarbons probably takes as long as tween larval hunger and feeding rate.…”

Chemical ecology involved in invasion success of the cuckoo bumblebee Psithyrus vestalis and in survival of workers of its host Bombus terrestris

“…After entering a host colony the parasite female is attacked by host workers that defend their nest against enemies-recognized through foreign scent-by hissing (Kirchner and Röschard 1999) and, of course, by stinging. Upon intrusion, the parasite tries to adopt (Fisher 1984b;Dronnet et al 2005) or imitate (Zimma et al 2004;Sramkova et al in preparation) the existing nest odour or use repellents (Zimma et al 2003) to reduce the attacks launched by the inhabiting workers.…”

“…This suggests that there is a species-specific and a colony-specific component to the odour (Fisher et al 1993;Dronnet et al 2005). It was proven that Psithyrus ashtoni recognize their host species by olfactory cues (Fisher 1983(Fisher , 1985, and Psithyrus rupestris use the trail pheromone laid by their Bombus lapidarius host workers to find the entrance to a nest (Cederberg 1983).…”