Figure 2.

Total ion gas chromatograms of the internal hydrocarbons extracted from Musca domestica females of various ages. For extraction of internal lipids, insects that had already been washed with hexane to remove external hydrocarbons, were immersed in 3 ml of chloroform/methanol (1:2 v/v) for 1 hour in an ultrasonic bath with ice, before extracting the internal lipids by the procedure of Bligh and Dyer (1959). The chloroform layer was evaporated under a gentle stream of nitrogen and the lipids taken up in 1 ml hexane to which 400 ng of n-C19 was added as an internal standard. Prior to GC-MS analysis the 5 samples from each age were pooled.