I found a small bristly caterpillar on Choke Cherry (Prunus virginiana). Also found a larger similar caterpillar on Alder (Alnus spp.). Brought them in and reared both on Choke Cherry. One caterpillar always stayed smaller than the other. Finally determined that they were Gypsy Moth larvae. The larger caterpillar started pupating by wrapping itself in leaves of its food plant, but I could see the pupa inside. The smaller larva started pupating later in the day. Thirteen days later the larger pupa eclosed to reveal a female Gypsy Moth. The next day the smaller pupa eclosed revealing a male Gypsy Moth. There had been some speculation from people who had looked at the pupae that they were different species, because of size difference. We were all surprised! NOTE: The pupae photos were taken AFTER the adults eclosed.