Sunday, October 21, 2018

A Couple of Weirdos

My last post here focused on the joys of National Moth Week, but what I neglected to mention was the added benefit of other insects being attracted to blacklights. Sometimes you get strange and significant surprises at your ultraviolet beacon. This is the story of two of those.

Clown beetle, Ulkeus intricatus, from Chico Basin Ranch

During our first moth week event at Chico Basin Ranch on July 21, we were all taking images of the moths that were drawn to our lights. There were plenty of other insects, too, like true bugs, flies, even a few wasps, plus lacewings, antlions, and beetles. I tried to document most everything, but it was not until I began editing my pictures that I noticed something spectacularly wierd. In one corner of an image of a moth was a beetle I recognized instantly as a "clown beetle" in the family Histeridae, but it had strange flanges on its legs and was a lot more bristly and "groovy" than the usual hister beetle.

It was reddish in color, too, while nearly all other clown beetles are jet black. I was aware that some clown beetles are found only in association with ants, and so I began looking at various species in the subfamily Hetaeriinae. Sure enough, up popped Ulkeus intricatus as the most likely suspect.

Legionary ants, Neivamyrmex sp., hosts of the clown beetle

So, now I begin researching this species, or at least the genus, to find out what its life history is like. It turns out that it is found only in the company of legionary ants in the genus Neivamyrmex, which makes things stranger still. Legionary ants are in a group of ants that includes army ants. They are nomadic, and mostly nocturnal, raiding the nests of other ants to prey on the larvae and pupae. This explains why the beetle was flying just after sunset: It was looking for a party of legionary ants and got distracted by our UV lights.

Exactly what the beetle does with, or to, the ants is largely unknown. My references say that the beetles are "guests" of the ants, which could mean anything from mutualism to kleptoparasitism (mutually beneficial relationship versus stealing the ant's food), or something else entirely. Exactly how the beetle would complete its life cycle if its host has no nest raises questions, too, though Neivamyrmex colonies are known to be sedentary over the winter.

Male legionary ants like this one fly to lights at night, too

There are six recognized species in the genus Ulkeus in the U.S., collectively ranging from North Carolina and Tennessee to Florida and west to Texas and Arizona. Five of those species are yet to be named and described, so I may be jumping the gun to assign a species to this one, especially since I never saw the thing let alone collected it. For all I know it is a seventh species.

Braconid wasp, Chrysopophthorus americanus

My wife and I put out a blacklight near Lyons, Colorado on July 22, despite cool and damp conditions, and among the many insects that flew in was a small, ghostly-looking wasp. I recognized that it was probably a member of the family Braconidae, wasps parasitic on other insects, but was baffled after that. Thankfully, there is Bugguide.net, and I started browsing the images to see if anyone else had recorded this wasp and, if so, was it identified.

Lo and behold, there it was, identified as Chrysopophthorus americanus. That almost never happens, being able to get a species identification that way. What's more, I learned that this wasp is a parasite of adult green lacewings (Neuroptera: Chrysopidae). Talk about a specialized niche. Since lacewings are often attracted to lights, it stands to reason that their parasites would be, too. Apparently the female wasp inserts her egg into the abdomen of the lacewing. The larva that hatches then feeds as an internal parasite inside the lacewing, eventually exiting to pupate.

Those beautiful emerald eyes!

What a wacky couple of "bugs." That is what I love about entomology, and natural history in general: You never know where one observation is going to take you, how one species intertwines with others....It is supposed to be a mild night here on October 21 and I am half-tempted to put the sheet and the blacklight out.

Sources: Caterino, Michael S. and Alexey K. Tishechkin. 2009. "A New North American Genus of Hetaeraiinae (Coleoptera: Histeridae), with Descriptions of Six New Species from the U.S.A. and Mexico," Zootaxa, 2311: 1-18.
Maxwell, John R., et al. 2008. "Species Chrysopophthorus americanus," Bugguide.

2 comments:

  1. Hi Eric, i confess i have not been here often, sometimes i forget. But your posts are very interesting. I am a hobbyist of butterflies and moths, and usually there are also interesting things which lead me to further learnings; e.g. mutualism of some larvae with ants. However, for moths i documented a lot but i know not much about them. I have long intended to buy lights to lure them but hasn't done yet for lack of time. And what are blacklights? What are they for? thanks.

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    1. I very much appreciate your visits here and your comments. Thank you! Blacklights are tube-shaped lights that shine in the ultraviolet spectrum, so they glow purple. Insects are drawn more toward that end of the light spectrum, though they will fly to "white light," too.

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