Last month, one of our captive Mantis religiosa shed its skin overnight and emerged as a full grown adult. Last night, our final mantis did the same, and we found it drying out its wings this morning, already much larger than its cast-off skin. This is a delicate, dangerous process, and even more dangerous in captivity. One of our textbooks, The Praying Mantids, has an entry in the index under “molting disaster,” listing the problem as one of the most common causes of death of captive mantids in the laboratory. No one’s sure what causes molting disasters in the lab, though it might be due to poor humidity or weird, artificial lighting, or just because of unusual stress on the nymphs due to their artificial environment.
The second most common cause of death among captive mantids is cannibalism. We found out about this today when we brought home two M. religiosa in the same container. Even though one of them had just had a big meal of a bee in the tall grass in Briones, where we were exploring this morning, it nevertheless must’ve still been hungry, because when we got home we had only one praying mantis in that container! Next time we will know better.