Scarlet Malachite Beetle

2009 January 10

Here’s another beetle with soft wing covers, that Sam caught in the house back on May 28, 2008. To make up for the nebulous identification of last week’s beetle (“some sort of soldier beetle”), this time I can be much more specific: it’s a Scarlet Malachite[1] Beetle, Malachius aeneus. Bug Guide actually has a list of characteristic features for this beetle, let’s see how it shapes up:

1. Black and red (black areas have greenish sheen in good light); elytra red with basal triangular black strip along inner margin, tapering to a point about two-thirds distance from base – Check

2. Face pale yellow or bone colored; – Check

3. Top of head black; pronotum black with small red patch at anterior lateral corners – Check

4. Abdomen black with thin white band at base of each segment, and pointed tip extending beyond elytra; legs and antennae black – Check (well, almost. The antennae got broken off at some point, and it’s kind of hard to tell what color they might have been.)

I have to say that, if that checklist is any good at all, then there is practically zero chance that I’ve misidentified this one.

These might be yet another introduced species, although if they were introduced, nobody seems to know exactly when they first arrived from Europe. It seems to me they are pretty common around here, I see them quite a bit, and they have colonized most of the northern US and southern Canada. They evidently live across wide swatches of Asia, too. I’m not finding a lot of information about them, mainly because they are not a crop pest and not of enough economic interest to arouse much study.

Most of the pages I do find for it are specific to England. It seems that in England they are quite rare, and dwindling in numbers. Among other things, and this may or may not have anything to do with their dwindling numbers, they like to hang out in thatched roofs. The English entomologists are using it as an example of an endangered species. So, in regions where scarlet malachite beetles are common hardly anybody pays attention to them. Meanwhile, a number of people are very interested in them in places where they are rare, but only because they are rare.

It sounds like they are similar to the soldier beetles in habits, in that they have predatory larvae and the adults mostly eat pollen and other insects. The adults only come out for a few weeks in early summer, and then it’s back to being grubs the rest of the time. I expect (but can’t prove) that the red color indicates that they have some noxious chemical secretion that keeps them from being eaten – again, that would be pretty typical.

So, to sum up: positive ID, rather pretty beetle, not much economic importance, poorly studied. Lots of room for elaboration, here.

*** Update *** Since originally posting this, we caught a beetle larva and reared it to adulthood, and it turned out to be one of these

[1] Malachite is a strongly green-colored copper carbonate mineral, which is a minor ore of copper that I occasionally work with in my day job as an extractive metallurgist. I personally think it is much greener than the greenish-black portion of this beetle, although “Scarlet Malachite Beetle” does sound much better than “Red Greenish-Black Beetle”

One Response
  1. January 10, 2009

    Another learning experience for me. As an added bonus, I now know what elytra are. Thanks!

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