Lygaeid Seed Bug Nymph

2008 September 20

This one is actually over a year old, it was found on the kitchen floor in early August of 2007. It’s a little guy, only a couple of millimeters long. It was hard to see details with the naked eye, and I thought at the time that it was some kind of beetle. But, when magnified we can see that it doesn’t quite look right to be a beetle::

First off, there are no wing covers (and, for that matter, no wings). It is therefore not an adult beetle. And, beetle larvae look more like grubs, while this one has very un-grub-like legs and antennae. Also, its antennae are reasonably long, but only consist of a few elongated segments, while beetle antennae usually have lots of short segments. So, I think we can scratch “beetles” off the list altogether.

From the underside, we can see that the legs are pretty long compared to its body, and it doesn’t have anything resembling mandibles. In fact, it seems to have piercing-sucking mouthparts, which we can see more clearly in the next picture (it’s the long, straight object starting at its head, and extending back between the legs):

The mouth parts and antennae pretty much clinch it as being a True Bug, suborder Heteroptera. The size and winglessness tell us that it is a nymph (immature) bug. True bugs have an “incomplete” metamorphosis, where the young ones look a lot like the adults except that they start out with no wings, with the wings gradually developing as it molts and grows. This is in contrast to the “complete” metamorphosis of things like flies, butterflies, and beetles, where the maggot/caterpillar/grub look little or nothing like the adults.

And this is the point where I got stuck and had to ask on Bug Guide to see what the experts had to say. Identifying a little nymph like this is tricky, because a lot of the features that are used to tell different kinds of bugs apart don’t develop until they are nearly adult. Based on the size, this one is very far from being adult, so it doesn’t have many distinctive features yet. The best anybody could do from the pictures[1] was that it was one of the Lygaeidae, or “seed bugs”. Of course, this was the old Lygaeidae family, the taxonomists have recently split out a bunch of things that used to be considered lygaeids into their own families [2]. If I had to pick which of the former Lygaeids is the most likely family for it now, I’d probably go with the Rhyparochrimidae, or “dirt-colored seed bugs”[3].

There are a lot of species of seed bugs, but they are (obviously) hard to tell apart, particularly when they are this young. The nymphs mainly live by getting into developing seeds of plants and sucking juices out of them. Some of them are flattened and shaped a lot like pine or spruce seeds, and the nymphs grow inside of pinecones, but this may or may not be one of those. Living inside a pine cone is a really good approach to life, because green pine cones are actually pretty good armor against predators if you can get inside them. There are spruce trees right outside the kitchen window that have a lot of cones, so that could easily be where this one came from.

Aside from destroying a fraction of the seeds in the plant, they evidently don’t have a lot of economic impact. Yet again, a bug doesn’t get a lot of attention when it doesn’t cost somebody a lot of money.

[1] The pictures are gone from Bug Guide now, because (a) they just weren’t getting identified beyond “some kind of seed bug”, and (b) the editors decided that they weren’t good enough quality to be worth keeping just as examples of a “true bug nymph”. I suppose they are right.

[2] Those nutty taxonomists. What wild lives they must lead. “Lumpers” duking it out with “Splitters” late into the twilight hours of the morning. . . . Although, to be fair, we are in a really unstable point in the taxonomy business. Until recently, they had to try to classify everything based entirely on what they looked like, which could be misleading when you had, say, cases of convergent evolution making things that were actually distantly related look closely related. Nowdays, though, they are using DNA analysis to see how closely related things really are, and they are finding out that a lot of the existing taxonomy is all wet. This is making the life of a taxonomist very complicated.

[3] But then, that’s just me. I’m probably completely wrong.

3 Responses
  1. September 26, 2008

    Really, Tim, you need to spend some time cleaning your bugs. This little guy is a mess! You should tell him to wash up for picture day. Just what will all the other bugs say when his photo is published in the yearbook?


  2. September 26, 2008

    Yeah, I know. Maybe I should make a scrub-brush for these guys to brush off the dust. Two millimeters is pretty small, though. Maybe a cat’s whisker would do – here, kitty, kitty, kitty . . .

  3. September 30, 2008

    No, we won’t be cutting off any whiskers over here, thank you very much!

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