Friday, June 20, 2014

Very Hungry Caterpillars

gypsy moth caterpillar (creative commons)
How much can a single caterpillar eat? A lot! Caterpillars are basically eating machines. They need to be if they hope to get through all those instars (larval stages), into a cocoon or chrysalis, and reach adulthood in time to mate or migrate.

One summer the gypsy moths were so numerous we could hear frass dropping on leaves like rain. Bits of leaves littered the ground - crumbs dropped by the herbivorous gluttons devouring our forest canopy. Reference books mentioned that gypsy moths could defoliate entire forests - but there was not one word on how much an individual caterpillar consumed.

So we decided to take prisoners and find out for ourselves. Or plan of action: give them leaves and see how much they eat over 24 hours. Sounded easy enough.... So we made up cozy homes cells for our captives, one caterpillar per gallon jar, and gave them leaves. Before feeding them, though, we traced each leaf onto a piece of centimeter graph paper. That made it easy to approximate leaf area by counting squares and parts thereof. The next day we took out what was left of the leaves and traced them. Now we could figure out how much they ate.

Summer is the perfect time to go caterpillar watching. And there are so many things to discover about caterpillars: what they like to eat, how they move, where they hang out in the hot part of the day...

Here are a couple of handy resources for budding caterpillarologists (people who study caterpillars):

Everyone needs a field guide, and Caterpillarology is full of hands-on ways to look at these guys.

Also check out  the Butterfly School.

Drop by STEM Friday to see what other science books and resources bloggers are sharing.   


  1. Hmmmm. My comment disappeared when I tried to publish it. First, I could hardly believe the photo of the gypsy moth caterpillar was real. I thought it was a piece of custom jewelry! Second, I had no idea caterpillars were such voracious eaters. You could hear the frass??? Wow. I really need to read up on these creatures. Thanks for such a fascinating post.

    1. Such beautiful caterpillars - and so destructive! And yes - we could hear the soft pitter of falling frass.... almost sounds like falling mist.