Three-spotted flea beetle

2007 November 17

This little beetle was found out back, crawling around in my father-in-law’s hunting blind[1].




At first, I figured this would be a hard one (there are at least tens of thousands of species of tiny beetles in North America, which one would it be?). But, there were two things that made it easier: the rather distinctive color pattern[2], and the fact that while I was carrying it in my hand, I could feel it jumping. Jumping is very unusual behavior for a beetle, and the hind legs on this specimen were certainly adapted for it



I mean, look at the thighs on that beetle! This certainly narrowed it down a lot, to one of the “Flea beetles” tribe Alticini. These are generally tiny beetles, and are considered a type of “leaf skeletonizing beetle” because of the way that they eat plant leaves – they basically chew holes in the leaves around the veins, leaving a porous leaf with all the green parts eaten out of it. Some flea beetles are plentiful enough to be significant crop pests. Unlike a lot of other crop-eating insects, it is the adult beetles that do most of the damage, although the larvae of most species evidently feed on the plant roots (which certainly isn’t going to do the plant much good either).

I think this is one of the beetles in the Disonycha genus. Based on the coloration of the head and thorax, and the pattern of black marks on the thorax, I think it is most likely Disonycha triangularis[5]. I’m not really finding a lot of information about this beetle, suggesting that it is not one of the flea beetles that are serious agricultural pests.I did find a site that mentions them as minor pests of alfalfa and beans, but they have to destroy 10-20% of the leaf surface before they affect plant yields, and are evidently unlikely to be a serious pest.

[1] It started out as a large packing crate that was thrown out by the University. I think it had an X-ray diffractometer in it originally. We hauled it home, and set it up at the back of the property, and most years he is able to shoot a deer[4] right there in our back yard. Every year, my father-in-law does some work on it and makes improvements, so now the original packing-crate core is practically unidentifiable. These days, it is sided with tarpaper, has a shingled roof and plexiglas windows, and almost looks like a permanent structure. I suppose the next thing it needs is electricity.

[2] If all I had to go on was the coloration, I might have misidentified it as one of the “pleasing fungus beetles”, some species of which have the red head/thorax and black body, but don’t have the jumping legs. Speaking of “pleasing fungus beetles”, that name always cracks me up. Somebody certainly liked them. There are also “handsome fungus beetles”, which is almost as good. I’m not sure why they got singled out as being particularly pleasing[3], it seems to me there are a lot of other equally good-looking beetles in the world.

[3] It makes me think of the guys on Mystery Science Theater saying “Do I please you? Do you find me pleasing?”

[4] And don’t give me any of that “Don’t shoot Bambi!” stuff. The deer around here are practically vermin, any garden or young fruit trees that aren’t behind a 6-foot fence they regard as their personal salad bar. They’ll walk right past all sorts of succulent trees that are big enough to take the abuse, and zero right in on the young fruit trees that we just planted so they can nip them right off. A co-worker referred to deer as “giant rats”, and I really can’t disagree with that. I mean, for the last couple of years they have even been eating the
leaves off of my rhubarb patch. Rhubarb leaves! Aren’t those supposed to be poisonous?

[5] Disonycha triangularis, the three-spotted flea beetle, is one of the over 1000 species of beetle discovered by Thomas Say in the early 1800s.

6 Responses
  1. MRL permalink
    February 11, 2008

    I have to ask – what does he do with the deer he shoots? I mean, even if they are pests, it seems like an awful waste of venison if he’s not using them.

  2. February 11, 2008

    Oh, he eats them, of course. My in-laws love venison, and my wife and I eat a lot of it, too. I suppose it’s actually a fair trade: they eat my crops, we eat some of them. It’s still annoying when they chew off a young apple tree to a nubbin, though.

  3. MRL permalink
    February 11, 2008

    Sounds like a fair enough trade to me. Have you maybe tried putting motion sensors by the apple trees? I’m afraid I don’t know much about deer habits or, for that matter, growing apples, but I’ve always heard that they’re fairly skittish, especially if they’re hunted around there.

  4. February 11, 2008

    They actually aren’t all that skittish, since they only get hunted for about one month per year. They seem to have figured out when the dangerous time is, and are pretty bold the rest of the time. One thing we have tried is “liquid fence”, a foul-smelling concoction that keeps them away a lot of the time, but doesn’t work 100%. The most reliable solution (which is unfortunately a lot of money and effort) is a fence at least 8 feet tall, preferably electrified. Some people who are serious about gardening around here have done that, and we probably will have to do it at some point too.

  5. October 29, 2008

    Please don’t forget to mention the danger of deer ticks. Ixodid (hard-bodied) ticks can be found just about anywhere deer can be found, and they can carry a number of nasty diseases: Lyme disease, bartonella, babesiosis, HGE, brucellosis, just to name a few.

  6. November 3, 2008

    Good point. So far, the only ticks we find around here in any quantity are wood ticks, like these, but the neighbors tell us that deer ticks are starting to be seen in the area. Some are claiming that the main danger of deer tick bites is in the fall, while the wood ticks mostly bite in the spring, so this might mean that we end up with ticks more or less continously. Wonderful.

Comments are closed.