The effects of laboratory culturing on (Z)-9-tricosene (muscalure) quantities on female houseflies

Using gas chromatography the relative amounts of (Z)‐9‐tricosene (muscalure) and some other hydrocarbons on the cuticle of 1‐ to 20‐day‐old houseflies (Musca domestica L.) from different strains were determined. Flies from a WHO strain, in culture since 1961, and first‐generation laboratory‐cultured flies from two wild‐type strains from a poultry breeding and a cow‐house with pigsty, respectively, were compared. On WHO females hydrocarbons with 23–25 C atoms constituted about 65% of the total hydrocarbons, whereas on wild‐type females less than 2% of these compounds was present. (Z)‐9‐tricosene comprised up to 20–30% of the total hydrocarbons on 5‐ to 20‐day‐old WHO females, whereas less than 0.5% (Z)‐9‐tricosene was present on the wild‐type females. We also compared the amounts of (Z)‐9‐tricosene and some other hydrocarbons on female houseflies, kept in culture in the laboratory for several generations. It appeared that whereas on first‐generation wild‐type females hardly or no (Z)‐9‐tricosene could be detected, the amounts of this substance had increased considerably after some tens of generations in the laboratory. It is suggested that this was due to selection in subsequent generations of high‐density populations. Production of (Z)‐9‐tricosene and of tricosane was shown to be closely linked. Selection did not affect the production of other cuticular hydrocarbons by the females. It is suggested that in mixed populations (both sexes together in a cage) in the course of time (Z)‐9‐tricosene is transferred from females to males and (Z)‐9‐heptacosene from males to females. It is concluded that reproductive ability of houseflies does not primarily depend on the amounts of (Z)‐9‐tricosene on females, although higher amounts of this substance may increase contacts between males and females.