Monarch caterpillars
Posted by Mrs. Penny Groth on September 20, 2007
Q: My class of 3rd graders raises monarch butterflies every year at this time. Recently I had a question I could not answer. Is ther a way to tell if a monarch caterpillar is a boy or a girl, or are they asexual until they become a butterfly? My guess is that they are asexual but I want to know for sure. thanks!
State: Indiana
A: To the best of my knowledge, there is no way to tell the sex of a Monarch caterpillar. At this stage in a Monarch's life (larva), there is no need for any kind of sexual differentiation. Although the gonads can be seen through the skin in some species of caterpillars- not in Monarchs,- I don't think there is any difference in male and female structure at this time in their development. Maybe a detailed dissection could determine this but not just a look. Of course, once a caterpillar becomes an adult, Monarch males have two black spots (one on each wing) on their hind wings that the females lack.
Your question is a good one, just one that I don't think science can answer or at least not without a great deal of effort. Thanks so much for sharing and I trust your students will enjoy their experience with the Monarchs.
John Wiessinger ( September 21, 2007)