Effect of age and sex on the production of internal and external hydrocarbons and pheromones in the housefly, Musca domestica

The epicuticular and internal waxes of male and female houseflies were examined by capillary gas chromatography-mass spectrometry at closely timed intervals from emergence until day-6 of adulthood. New components identified included tricosan-10-one, 9,10-epoxyheptacosane, heptacosen-12-one, a series of odd-carbon numbered dienes from C31 to C39, several positional isomers of monoenes including (Z)-9- and 7-pentacosene and a number of methyl- and dimethylalkanes. (Z)-9-tricosene appears in internal lipids prior to appearing on the surface of the insect, suggesting that it is transported in the hemolymph to its site of deposition on the epicuticle. The large increases in the amount of (Z)-9-tricosene in females from day-2 until day-6 is compensated for by a concomitant decrease in (Z)-9-heptacosene. The C23 epoxide and ketone only appear in females after the production of (Z)-9-tricosene is induced, and are only abundant in epicuticular waxes, suggesting they are formed after (Z)-9-tricosene is transported to the cells which are involved in taking them to the surface of the insect. Mathematical analysis indicated that the time shift between internal production and external accumulation in females is more than 24 h. The divergence between male and female lipid production occurs at an early stage, when insects are less than one day old.