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Hi Louis


Other than often supposed, the sex of an animal (both insects and all the way up to mammals) is not determined by their chromosomes, but by their hormons. And of course, the making of hormons is, in principal, regulated by chromosoms via for instance the hypothalamus in mammals.
However, from time to time, this system fails (for mammals is the embryonal stage the relevant stage), producing 'intersex' or even 'opposite sex'. For instance, the actress Jamie Lee Curtis is supposed to be a chromosomal male.
The big difference between insects and mammals is, that in mammals there is a constant rate of hormons, due to the blood circulation. However, this circulation in insects is much worse, so that the hormon level may differ from spot to spot. So, an insect can be female with male wing tip (very illustrative in the orangetipped butterfly), or any combination you like.

Pollution, for instance by Cadmium, is known to result into a high rate of intersexes. Intersexes, when you look for them, are not really rare. In Tachinids, at least every one out of 1000 is an intersex in some sort.


Theo Zeegers