A beetle from summer

When I returned to my parents’ this week my mom had brought out a beetle she had found while shopping downtown in the local town back in the summer, following a conversation we’d had earlier this week on a subject I can’t recall now. The beetle was dead when she found it, so she picked it up and brought it home with her. It was a warm reddish-tan, with large black spots down each side of the carapace, and one in the middle of the back. It’s obviously a member of the scarab beetles family, and further research revealed it to be a Grapevine Beetle, Pelidnota punctata.

Ordinarily a dead beetle on the sidewalk would probably have been passed by unnoticed, but the size of this particular beetle was what caught her eye. Below is an image of the beetle posed with a (live) ladybug for comparison. The scarab family contains 1300 species, some of them the largest beetles in North America. Grapevine Beetles can grow up to an inch long, which is not quite up to the six inches of the southern Hercules Beetle, but is still a pretty impressive beetle for this part of the country.

I’ve never seen this beetle alive myself; in fact, this is the first time I’ve seen it ever, which seems somewhat unusual for what looks like it should be a rather conspicuous bug. It seems fairly common, occuring through most of the east from Ontario south to northern Florida and west to Nebraska. The adults can be found from May to August through much of its range, and will regularly come to lights in the summer.

It inhabits deciduous forests. Adults feed on the foliage and fruit of grapevines (hence the species’ common name), but appear to do little serious damage. It lays its eggs in the summer on decaying logs, which the larva feed on during their development. Larva overwinter in the logs, pupating and emerging as adults in the spring. I found one site that offered care information for the species, but aside from a couple comments on the web, couldn’t see any evidence that it was frequently kept in captivity.

One of the features of scarabs is their club-like antennae. You can sort of see here that the club is actually many-parted. These plates are called lamellae, and the beetle can fan them out when sensing odours. When it’s not testing the air, it folds them up out of the way. This individual’s a little dusty from sitting on a shelf since the summer, but in this and the previous photo you can also see the mouthparts it uses to cut bits of vegetation. In the previous photo you can get a better view of the upper cutting mandibles, and the lower manipulating ones.

Beetles, like many insects, have hairy legs and bodies, under their smooth carapaces. These hairs are called setae, and are used for sensing the environment. Generally they sense small changes in air pressure.

Take a look at the claws at the end of this guy’s feet. The claws are primarily used to help the beetle secure itself to whatever it’s walking on. However, in scarabs the front claws are modified for digging. You can see how much more curved they are on this individual. Grapevine Beetles aren’t really diggers the way some scarabs are (such as dung beetles), but they retain the characteristics of the group.

In looking up information on beetle feet, I discovered this site that is doing research on the applications of beetle-foot design to modern technology. One of the main things they’ve developed from it is an adhesive that’s twice as sticky as glue-based tapes, and is reusable simply by washing with soap and water. I wasn’t quite clear on the specifics of the technology from their description, but it uses the principle of a beetle’s hairy feet (I gather this is a characteristic of a different family of beetles), which act like a thousand little suction cups on long threads. The suction cups adhere to the surface, while the long threads allow dust motes and other debris to slip between the affixing surfaces, so it can attach to dusty and dirty surfaces as well. The lab’s site has videos of their Mini-Whegs robots scaling vertical glass walls using the adhesive. I’m on dial-up while here at my parents’, so wasn’t able to watch them, but even just the idea is pretty cool.