Monday, July 2, 2012

Tortoise beetles

What: A few years ago I was looking through Audobon's guide to insects and I came across a photo of a tortoise beetle. They're hilariously improbable looking animals, somehow a cross between a lady beetle and an adorable, cartoonish turtle, and I immediately wanted to find one. I had to wait, and it wasn't until last year that my patience was rewarded. When I spotted it I dashed inside to grab my camera and when I came back it had vanished. Last week I was out at Rock Point at the marching band meadow, which is just full of milkweed, and I spotted an amazing type of tortoise beetle. It was a metallic silver, not very camouflaged on the underside of the milkweed leaf. As soon as I got close it popped off. I spotted a few more and the same thing happened every time.
I've been transplanting milkweed (Asclepias sp.) and intermediate dogbane (Apocynum cannabinum, apo=away from, cynum=dog, like canine, in reference to its toxicity to dogs and cannabinum in reference to its similarity to hemp for use in making cordage) to my front yard for a couple of years now (it's my fiber garden). Yesterday while hanging out on my front yard I spotted a mottled tortoise beetle (Deloyala guttata) on our morning glory vines. Mottled tortoise beetles are common on morning glories (Ipomoea purpurea, in the same genus as sweet potato) and its relatives (in the family Convolvulaceae). I grabbed my camera and took some shots and the below video of the little guy taking flight. 
A couple minutes later I was showing Zac the milkweed seedlings when I spotted another!! tortoise beetle. This one, a golden tortoise beetle (Charidotella sexpunctata), quietly deposited a chunk of frass (the entomologists delicate word for bug poop), and after a minute flew off. 
Ecological notes: Tortoise beetles are part of the leaf beetle family (Chrysomelidae). On the whole this group superficially resembles lady beetles. They're strict vegetarians, both as larvae and adults, and are often host specific to their food of choice. They over winter as adults, and as I noted above, when disturbed will just drop off the plant. I've seen this repeatedly with the simple and charismatic milkweed leaf beetle (Labidomera clivicollis), a common leaf beetle that feeds on the toxic sap of milkweed and has the exact same coloration as a monarch butterfly; if it shows up in my fiber garden I'll be sure to post a photo. Larvae will cover themselves in fecal matter to hide from would-be predators - not sure I'd go hunting for piles of poop.

Where: My frontyard.

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