Hello all,

I had a culture of Bacillus rossius, a while ago.  The eggs came from the
same batch, and the nymphs were kept in exactly the same way: same temperature,
same humidity level, even fed on the same food plants.  Still many individuals
would show different colours, which were visible from early instars on: light
brown, dark brown, reddish brown and bright green.  You can see pics on: http://www.wandelendetakken.be/soortlijst/psg03.htm

I agree that especially humidity has some influence on the coloration of a
stick insect.  But from what I have been watching, I would only speak of a
slight difference in colour intensity (not a real colour change), which is
occuring rather quickly and which is temporary.  Eg if you just sprayed, a light
brown female will soon turn into a darker brown, or a reddish brown one will
become almost red.  When humidity level decreases, they will become lighter
again. 

But a brown individual will never become bright green, whatever you change in
its conditions or food. 

Than I isolated the green females and their eggs to see what would happen
with the nymphs.  It appeared that more green females turned up in this culture
than in the one originating from eggs of brown females.

Another example:  sometimes yellow females appear in Heteropteryx dilatata
cultures, whereas the majority of the adult females is bright green.  http://www.wandelendetakken.be/soortlijst/psg18.htm

I isolated the yellow females and their eggs again.  It appeared that the
rate of yellow females in the yellow culture was much higher than in the green
culture, which were sisters of the yellow females.   Could it not be, that not
living circumstances and food cause such colour variations, but that this is a
genetical issue?  The reason for this genetical variation would be clear: a
survival tactic of the species, eg providing better camouflage in a changed
environment.

best regards,

Mieke