Beetle Bonanza

It turns out I had not been paying enough attention to the route we had taken the first time, and so on Thursday I became hopelessly lost. I phoned my wife and she informed me I was nowhere near the right road. Consequently, I got to the site in the late morning. When I arrived, there was no one to be seen. I looked around anyway, as there were also no postings against trespassing.

The first insects I saw were what I expected: medium-sized jewel beetles, Chrysobothris dentipes, as depicted above. These members of the family Buprestidae look exactly like little shards of pine bark, but they move often enough to be easily seen. Several males were engaging in “butt-thumping” displays to nearby females. Below is a very brief video depicting this. It is surprisingly audible, and also hilarious. I hope to go back again and get a longer video segment.

Also present were a fair number of the magnificent metallic green Phaenops gentilis. Though they are only about 8 millimeters in length, these buprestids are still conspicuous. Like most jewel beetles they are quick to fly when disturbed, though they usually simply run so erratically as to be nearly impossible to get an image of. Females pause often to lay eggs, though, so that is your one opportunity. The one below took time to groom itself and luckily I was in the right place at the right time.

While I was photographing another insect, I glanced down to see a very large buprestid that had landed on my shoulder. I grabbed it, and it turned out to be a Western Sculptured Pine Borer, Chalcophora angusticollis. Measuring 20-33 millimeters, they are among our largest jewel beetles. When they fly, the lifted elytra (wing covers) expose a bright blue, green, or violet abdomen. I brought it, and another specimen, home to photograph.

What surprised me most were the large numbers of predatory checkered beetles, family Cleridae, active hunters of bark beetles and other small insects. I thought that I was seeing one species, with individuals of varying sizes, but upon looking at my images it became apparent there were three species.

Enoclerus moestus was the first one I came across. E. lecontei was likewise common.

Lastly, the largest species was the “Red-bellied Clerid,” E. sphegeus. While the adult beetles will kill and consume a variety of other insects, the larvae appear to prey exclusively on bark beetle larvae. You know, like the Mountain Pine Beetle and its relatives that are often blamed for killing entire forests.

Longhorned beetles were present on the log stacks as well. I expected the White-spotted Sawyer, Monochamus scutellatus, and indeed I found a couple of females, one of them ovipositing, and a single male. These are large beetles that live up to the longhorn name. Their antennae are exceptionally long, especially in the males.

The most abundant of the longhorns, though, were flower longhorns in the genus Grammoptera. I even found a pair mating.

The freak of the longhorn show was the Ribbed Pine Borer, Rhagium inquisitor. The adults look very little like a typical longhorned beetle, having quite short antennae. Two specimens landed on me or in my vicinity.

They are medium-sized at 12-15 millimeters in body length. They get their name from the woven wreath-like ring consisting of coarse wood fibers that the larva creates for its pupal chamber.

I also found a few oddball beetles including a very tiny weevil, Lechriops californica. At least that is what I think it is. They bore, in the larval stage, under the bark on the trunk and larger branches of various pines.

Another predatory beetle was a very small clown beetle, family Histeridae. It may belong to the genus Platysoma, which live under bark and hunt the larvae of flies and beetles.

There were non-beetle insects, too, of course. The most common were the syrphid fly Chalcosyrphus piger. Females were alighting on the logs, presumably to oviposit (lay eggs) there. The larvae of these flies feed on decaying wood, and perhaps fermenting sap.

The most exciting find was a female aulacid wasp, family Aulacidae, in the genus Pristaulacus. They are easily mistaken for ichneumon wasps at first glance, but the ovipositor is downcurved at the tip; and the abdomen is connected high on the back of the thorax. These wasps are more closely allied to ensign wasps (Evaniidae) and carrot wasps (Gasteruptiidae). They are parasites of wood-boring beetles, surprise, surprise.

I am looking forward to returning to this site, as long as I am welcome. Those towering stacks of big pine logs are a bit intimidating, I have to admit, but worth braving for the bounty of beetles.

Sources: Cowan, B.D. and W.P. Nagel. 1965. “Predators of the Douglas-Fir Beetle in Western Oregon,” Technical Bulletin 86, Agricultural Experiment Station, Oregon State University, Corvallis, Oregon. 32 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. Miscellaneous Publication No. 1339, U.S. Department of Agriculture, Forest Service, Washington, DC. 654 pp.
Smith, David R. 1996. “Aulacidae (Hymenoptera) in the Mid-Atlantic States, with a Key to Species of Eastern North America,” Proc. Entomol. Soc. Wash.. 98(2): 274-291.