Mites as matchmakers: semiochemicals from host-associated mites attract both sexes of the parasitoid Lariophagus distinguendus.

Abstract

The role of volatile chemicals used for mate finding was studied for males of Lariophagus distinguendus (Forst.), a parasitoid of the granary weevil Sitophilus granarius (L.). In bioassays that used a static four-chamber olfactometer, males were attracted by host feces, hexane extracts from host feces, and volatile extracts of the feces obtained by closed-loop stripping (CLS). On the other hand, volatiles emitted by unmated females did not elicit any preferences in males. Both sexes of L. distinguendus responded to a synthetic mixture of neral, geranial, neryl formate, and tridecane occurring in the investigated extracts. All compounds are common constituents of astigmatid mites that are often associated with possible hosts of L. distinguendus. In the system investigated, all main compounds found in CLS extracts from larval feces of S. granarius are due to the mold mite Tyrophagus putrescentiae (Schrank) that uses neral, geranial, and neryl formate as an alarm pheromone. The possible role of host-associated astigmatid mites in mate and host finding of L. distinguendus is discussed.