The Unglamorous Life of a Tiny Hermit

One day last summer after I had been out in my prairie garden, I found a strange little insect clinging to my clothing. It appeared to be living in a rigid little case, carrying this shell-like enclosure as it walked about. I had never heard of such a creature. I knew about caddis flies, whose larvae build cases out of small sticks or stones, but they are aquatic, and there was little water in the prairie garden on that dry summer day. To have some hope of figuring out what this tiny creature was, I tried to get a few pictures of it, though I'm not yet well equipped for macro photography on the scale of this bug, which was only about an eighth of an inch long -- including its case. I managed to get a few shots that I could crop down to images that would serve as fair portraits, despite rather poor focus. Here's one of them:


I really had no idea what this was, or even whether its little case was something it constructed, or something (maybe a seed pod) that it had just moved into, as a hermit crab does with a shell it finds. I posted my few photos on smugmug, hoping that someone I knew might have some ideas, but we had little to go on.

This summer I found more of these little beasts, all of them perched on goldenrod plants in the garden. I did some searching of Internet insect-identification sites such as www.whatsthatbug.com and bugguide.net, but I didn't manage to find what I was looking for. I did get a few somewhat-improved photos. In the first one below, I'm holding the case between my fingertips, and the insect is extended pretty far, investigating its entrapment. In the second, it's walking across the palm of my hand.


A few weeks ago, my son John (a biology grad student) was in town, and he managed to find information about insects known as casebearers, a subfamily (Cryptocephalinae) of leaf beetles whose photos and descriptions matched my little hexapod friends. The larvae of these beetles do indeed construct and live in cases -- made out of their fecal matter!

Some of these casebearers belong to a group known as warty leaf beetles (the tribe Chlamisini), and the photos of the adults in this group looked familiar. I had seen one or two similar beetles on the same goldenrod plants, so we concluded that our casebearers were maturing into these adult beetles, leaving their ignoble enclosures behind. But these adults are hardly more glamorous than in their earlier form. They are small, dark, and lumpy-looking, as the next photo shows:


Descriptions of these bumpy little beasts note that they resemble frass (an entomological euphemism for caterpillar droppings), and one writer claimed he had seen bits of frass in insect collections, mounted and labeled as warty leaf beetles. This humble disguise presumably provides these little creatures with some protection from being consumed.

I still don't know precisely what species I've got in my garden, as there are dozens of species of warty leaf beetles in several genera. Most feed on particular kinds of plants, but it seems that goldenrods host a number of species. Nevertheless, I'm happy to know the "tribe" they belong to, and to have learned a little more about these humble creatures that advance from living in droppings to merely looking like droppings.

Posted: Sun - July 29, 2007 at 03:27 PM       by email

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