Do Saturniidae larvae need sunlight?

I bred a saturniid larva (Orthogoniptilum mucronatum) that made the diffeence between day and night ! During the day it stayed on the treetrunk and come to feed on the foliage during the night.
(ps : I suspect it was one of the reason that nobody collected it before as the caterpilar is very cryptic on the tree trunk).
One can suppose that it is a kind of dependance of the light.
Thierry

If you speak specifically about sunlight rays, in my experience it is not necssary !
I bred many inside black plactic bag (40-60 l) during their complete cycle (or nearly so) with success ! this concern Saturniid, Sphingid, papilioid, Cymothoe, Euphaedra, etc....
Thierry

In my experience also with indoor (dark conditions) and natural conditions i didn't notice major differences on the saturniids but , and this is only speaking of experience, the pigmentation of some species ,the average weight and the growing speed were influenced. Generally i believe that as with most of the organisms , specific metabolic procedures are strongly related to sun radiation. It's not only the photoperiod that you have to worry about. I almost always get optimum results with more "natural" conditions. Apparently certain types of diseases are easier established in boxes due to compromised immune systems . By the way watch out humidity as well, can be an enemy ..

An example of a caterpillar variation which i suspect that is due to reduced sunlight is this a.luna, which i like to call "the strawberry edition"

imageshack.us/photo/my-images/155/strawberryy.jpg/

in many cases, more slowly the larva grows more big it will be and low temperature slows the growth ! ... of course no artic temp !!!

true, growing slower creates sometimes bigger larvae. On the other hand thought you can get many losses ,especially with tropical species. Autumn / winter rearings on evergreen trees/shrubs usually don;t give that great results since even if the plants keep their leaves their chemical composition changes (a form of diapause too) so the nutritional complex ,important for the larvae, is being altered. Good bloodlines and livestock always give the best of the results ,rule of thumb!

I haven't noticed a difference between UV exposed and indoor reared Saturniids either.

It's interesting that you note the slowed growth from cooler temperatures results in larger imagos, I just tested that hypothesis this year for a few species and it did indeed prove correct, very pronounced in some cases. Here in Florida it's very easy to get extra high temperatures but cool is only available in an air-controlled room. So I reared some in the moth house outside and some indoors. One species in particular went from adult eclosure all the way through pupae again in just under a month when reared outdoors but returned tiny adults. The indoor counterparts took twice that long and were of average to large size. There is about 15-20 degrees (F) difference in temperature between indoor and outdoor on average though they do become closer overnight of course.

For me, the relative term "cooler" is 75-78 degrees while "warmer" is 90-95 average, ranging from 75-100 over a 24 hour period on average. Cooler temps were indoors so the temperature would have been constant. There are other variables that could be controlled better (for example humidity outdoors is 85%+ pretty much all the time, supplementing to that degree indoors is challenging if you still want to maintain good circulation) but it was a fairly promising pilot experiment that begs for further investigation.

I'd love to know if anyone else has tried anything like this and what they observed.