Sex pheromones in three Bradysia species (Dipt., Sciaridae): novel bioassays with female body extracts and fractions

Females of the fungus gnat species Bradysia difformis, Bradysia optata and Bradysia tilicola are able to produce sexual attractants. In males, the female extracts elicit species-specific courtship behaviour and attraction in an olfactometer bioassay. Attractiveness of the sex pheromone extracts seems to differ in the investigated species, being highly attractive for males in B. difformis and only moderately attractive in B. tilicola. Female B. difformis are attractive from late pupal stages until death of the imago. In contrast, female B. optata and B. tilicola are not attractive to males before emergence from the pupa and attractiveness decreases in older females. The pheromones seem to be located on the surface of several body compartments of freshly emerged females. Sexual pheromones of all three species represent multicomponent blends and can be separated in several fractions via thin layer chromatography (TLC). Males of all species show courtship behaviour when placed on developed TLC sheets, indicating the position of the biologically active compounds. In B. difformis and B. optata, the most non-polar TLC fraction is attractive to males, whereas the single fractions of B. tilicola-pheromone elicited almost no attraction of males.