instar number in insects

[Toomas Tammaru]

Dear colleague,

	we have a question concerning variability of INSTAR number in 
INSECTS.

         We are currently working on a review on intraspecific variability
(plasticity) in the number of larval instars in insects. In our paper, we
ask in which insects, and under which conditions, the number of larval 
instars varies and what are the consequences of this variability in the 
context of life history evolution.
         We have compiled a data base of works reporting variability in
instar number but it appears to be really complicated to find papers which
state that there is NO variation. However, this may be simply because 
invariability is not reported.

We are therefore asking for your help in finding such observations.

	- do you know of insect species in which, despite of _extensive_
ecological work having been carried out (insects subjected to various
conditions), there is NO EVIDENCE of intraspecific variability in instar
number?
	- do you know of cases in which intraspecific INVARIABILITY of instar
number is generally considered characteristic of some taxonomic group
among insects?

If you think that you could help us with information, may we ask to reply 
to Toomas Esperk at tome at ut.ee. Your contribution will be duly 
acknowledged.

		With many thanks in advance

			Toomas Esperk and Toomas Tammaru, University of Tartu, Estonia;
			Sören Nylin, Stockholm University, Sweden.