More belostomatids

I mentioned in my last post that water bugs from the family Belostomatidae are among the most common insects at the Solite Quarry. Christina was recently photographing a rather nondescript piece of the insect bed that demonstrates this quite well.

At first glance there doesn’t seem to be a whole lot here. The silver line cutting diagonally across the rock is a fossil plant stem. These fragments are exceedingly common at Solite, but they’re generally unidentifiable and we don’t pay a lot of attention to them (although many of the Solite plants are well preserved and extremely interesting). But if you look closely at the lower half of the stem, there are some other silvery objects beside and under it. Almost all of these are belostomatids; in fact, there are at least 15 of them on this one rock:

The belostomatids here run the gamut, from tiny nymphs that are only a few millimeters long, to older nymphs that are as much as 1 cm long (note the beautiful frilly swimming legs):

Here’s one especially rich patch; how many belostomatids are in this picture?

At least four! Each is outlined below in a different color. We think the different sizes are just different age nymphs:

 

Hiding directly under the stem is an adult belostomatid:

In case you’re having trouble seeing it, below is a marked up version. It appears to be preserved dorsal-side up. Legs are outlined in red, a wing in green, and yellow marks the pronotum and possibly part of the head. There’s also a large nymph in the lower right corner.

This accumulation is pretty interesting, as this kind of density is not typical of the insect bed. Modern belostomatids are predators, so it seems unlikely that they were eating the plant (although we’re assuming that these belostomatids had the same dietary preferences their modern relatives). Maybe they were resting on the stem, using it as a jumping-off point to attack their prey. If so, that seems a risky move for the tiny nymphs. Adult notonectids, which are also water bugs, are known to occasionally eat nymphs of their own species. I wouldn’t be surprised if belostomatids are also at least occasionally cannibalistic.

Of course, another possibility is that this is a death assemblage caused by surface tension effects. If the plant fragment was floating on the surface next to a bunch of dead water bugs and they came into contact, surface tension might hold the whole assemblage together long enough for it to land on the bottom and get buried.

Whatever the explanation is, it demonstrates that there are lots of small puzzles at Solite waiting to be answered.

If you want to see all 15 of these belostomatids, images of them are now available on our online database.