I haven’t spent much time in the field this summer. The last 6 or 7 years, I’ve had summer field work tied to grants; this year, my grants involve sitting in front of the computer. But over the holiday weekend Kingfisher and I got out a bit to do some general exploring. At one spot, he called me over to look at this curious insect. At first glance, he thought it was a gall on a leaf…until it moved.
It turns out this is the larvae of a leaf beetle in the subfamily Cryptocephalinae, known as the casebearers. The case the larva is toting around is made from its own excrement, a good way to become unobtrusive and unappealing to predators while in a vulnerable state (I always say). According to the incredible book Insects: Their Natural History and Diversity: With a Photographic Guide to Insects of Eastern North America:
“Leaf beetle larvae in several subfamilies use their own excrement to form protective shields or coverings, but larvae in the subfamily Cryptocephalinae carry this habit to an extreme. The eggs hatch under a fecal blanket and proceed to use their own waste to make a case that is added to as they grow.”
The adult beetles are quite attractive, reward for spending the beginning of their lives covered in their own crap. This one was feeding on Rubus, there’s a possibility it may be Chrytocephalus venustus.