Last week I came across this bumpy beetle on a goldenrod (Solidago sp., Asteraceae) in a southeast Michigan meadow. I got this one clear shot and then tried to capture it, but it dropped to the ground and I couldn’t find it. It seems like a lot of beetles do that to escape a threat. I swept the area over the next few days but couldn’t find another one.
I did however find a lot of these interesting structures:
I assumed these blobs were either frass (poop) or pupae of some insect. Thanks to some help from bugguide.net, I learned they’re sort of a little of both. These are, in fact, the larvae of the bumpy beetle in the first picture. Upon hatching these young beetles construct cases made from their own fecal matter. Appropriately, these are known as case-bearing leaf beetles (Chrysomelidae: Cryptocephalinae). More specifically, the beetles shown here are warty leaf beetles (tribe Chlamisini).
I went back the other day to collect some more of these larvae and take them apart. Here you can see the larva peeking out of the case:
They appear to be curled up inside the case:
And here it is free from the case:
I thought this was a pretty cool find. I never knew there were beetles that grew up inside cases made from their own poop who later emerge as intricately bumpy adults.