Black beetle with orange patches under wings – Blister beetle

2014 September 13

Our dog found this one in the woods on August 20, 2013. It must have smelled pretty strongly to her to draw attention like that. It is clearly a relative of the Oil beetles that we’ve found several times in the past, except that this one appears to have wings long enough to be fully functional.

It was a middling-sized beetle, as we can see from this shot of it on my fingertip.

For further handling, I switched to the flexible “insect tweezers”, which are designed to hold insects without crushing them. The reason for the switch was that this is clearly some type of blister beetle, and a lot of blister beetles ooze a blistering agent from their joints when they are roughly handled. And who needs blisters?

There were orange patches on the sides, running up under the wing covers. I didn’t get a look at whether the entire top of the abdomen was orange under there, or just the sides.

The only blister beetle pictures I found that were black, with the pale margins around the wing edges, and the orange patch on the abdomen were certain beetles in the Epicauta cinerea species group. This is a group of about twelve species (six found in the US) that evidently have variable color forms ranging from completely black to dark with pronounced white margins. The bulging abdomen on this specimen looks like it is an egg-filled female.

Most of the beetles in this genus lay eggs on grasshopper egg clusters, although some of them attack other blister beetle eggs and larvae. They have the blistering agent “cantharidin” in their bodies, which is quite toxic, and livestock like cattle and horses have been known to die from eating hay with blister beetles baled into it. So it’s a good thing Sandy took this one away from our dog before she could eat it.

2 Responses
  1. September 13, 2014

    I’ve probably asked this before, but have you considered posting YouTube videos of these beasties? Seeing it in the tweezers made me think of the little legs angrily swimming in the air.

  2. September 16, 2014

    Up until now, video hasn’t been an option, because while my Canon 10D has many useful features, shooting video isn’t one of them, and our point-and-shoot wasn’t much good at close-up work.

    But, I did just buy an Olympus TG-3, which has both the ability to shoot video, and pretty good macro capability. There may be more videos in the future.

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