Black and Yellow Longhorn Beetle
When Sam caught this beetle in July of 2010, I just took the pictures for the sake of the practice, because I though that it was one that had already been photographed and posted on this site. But, on further examination, I see that aside from both being black beetles with yellow markings, they were not otherwise very similar. The other one had very thin, sharply curved yellow markings, while this one has broad yellow stripes, with the middle stripes joining to make a kind of “U” mark on each wing cover.
This looked fairly distinctive, and after some rummaging around on BugGuide, it looks like one of the Flower Longhorns in the genus Typocerus.
Specifically, I think it’s Typocerus sparsus, which is evidently specifically found in the Great Lakes region. In which case, it is as close to a species endemic to this area (that is, found here and nowhere else) as we have caught to date.
Like other non-wasp insects that hang around flowers and have black-and-yellow markings, these beetles are almost certainly wasp mimics. As usual, it is believed that they are trying to convince potential predators that they are packing a sting. As far as anyone knows, they are actually harmless. But after finding out that even some insects that are commonly believed to be simply mimicking other, more dangerous/distasteful insects are actually dangerous/distasteful in their own right, I’m not so sure I believe that these are completely harmless without some evidence. Unless somebody tastes one of these beetles and declares it edible, I’m going to suspect that there is a good possibility that they have some nasty chemical defenses themselves. Or at least are able to give a nasty pinch.
That said, they do look a lot like wasps when they fly, so anybody who reflexively avoids wasps will probably shy away from these beetles in flight, too.
Like other longhorn beetles, their larvae bore into decaying wood, although I don’t think this particular species has been studied enough to know their wood preferences. Their relatives seem to like rotting pine, though.
Note added on March 13, 2013 for readers in the Southwest: With the number of people commenting below that they found a similar beetle in Texas, and that they got a painful sting/bite from it, I figured I’d better look into this.
In general, beetles that look like mine really are other, related wood-boring beetles. And if they seem to be associated with firewood, then that’s almost certainly what they are. But, in the southwest, another possibility is this similarly-colored blister beetle, (although they are not closely related). Blister beetles have a strong blistering agent (cantharidin) in their “blood”. When they are crushed, or feel threatened, they will bleed this on you and apparently raise painful blisters. They are very toxic if eaten, too (some blister beetles have been known to kill horses when they got baled up into hay that the horses then ate).
So, if you live in or near Texas, and see a beetle similar to this, don’t handle it, and don’t squash it. And definitely don’t eat it!