Do Saturniidae larvae need sunlight?

Actually the metamorphosis of lepidoptera (from ovum to imago) is strongly governed by their environment (temperature, humidity, air flow, photo period, available resources, etc). That's why I designed all of my rearing/breeding cages and plant storage methods so I could control all of the environmental factors to match the normal conditions during the peak seasons of a species. Short photo period slows them down, can induce early aestivation/hibernation, both that can result in smaller livestock/imago's. How sever is dependent on the species and the conditions. I've reared a lot of different species of Saturniidae since 1964, and they are a product of their environment same as they are from all lepidopteran families. FWIW - HTH

Photo period refers to the number of hours per day they are exposed to light, not what kind of light, and they adjust their metamorphosis to it. IMO all living things benefit from actual sunlight, whether direct or indirect. With caterpillars the best scenario is to place cages so they can move freely in and out of direct sun light to regulate their own temperature though. That said, they do just fine with only artificial light. What type of light is speculative IMO, I've used all types with good success. I used timers on my cages to run lights to get the photo period I wanted, so they got both artificial and natural light during a day for the photo period I set for them.

Both larva and pupa can be fooled by regulating their environmental factors to make them respond to whatever season you want them to regardless of what time of the year it is. In part how I reared larva of continuous generations of some species year-round even those years I lived in the deep snow frozen north, and high elevation arctic/alpine species for many months past their normal season in the wild. The only limiting factor was larval food plants that could be kept viable, and how long they could be kept. With some plants I devised ways to keep them all winter long, so could rear all winter. I also could force some biennial species to be at least annual just by altering their environmental factors. While it may not be "nice to fool Mother Nature", doing so can be very beneficial to rearing projects.

FWIW