Free University of Berlin, Institute of Biology, Applied Zoology / Animal Ecology, Haderslebener Str. 9, 12163 Berlin, Germany.
The male courtship behavior in L. distinguendus starts with a characteristic wing fanning mediated by a female derived sex pheromone. The pheromone is produced already in the late pupal stage and is active only in the direct proximity of the females (0-5 mm). For chemical orientation over longer distances males of L. distinguendus use the same chemical cues as the females use for host location. These cues are located in the faeces of their host, the granary weevil Sitophilus granarius. Chemical analyses revealed that most of the volatiles in the faeces are due to the host-associated astigmatid mite Tyrophagus putrescentiae. A synthetic mixture of neral, geranial, neryl formate, and tridecane occurring in the mites attracted both sexes of L. distinguendus in an olfactometer bioassay. Massive infestation of stored grain by granary weevils can cause restricted sites of high temperature and humidity (hot spots), conditions that favor secondary infestation by astigmatid mites. Thus, responding to volatiles emitted by host-associated mites benefits both sexes of L. distinguendus as this behavior facilitates the location of mates and areas of high host density.