Tierra de Oro Laboratory

Physiology and Ecology in the Pinyon-Juniper Savannah

Life in the Frigid Wastes

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Dave

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Arthropods Active in the Cold

Field with small trees, bushes, and grasses, covered in a few inches of snow.
Pitfall trap array after a night of snowfall. The blue flags marking the locations are visible, but the traps are difficult to find. 3/8/25.

The pitfall traps were set this month with the expectation that it would be too cold for small arthropods to be active. The data would serve as a baseline for later surveys, when bugs would be more active. As if to emphasize this point, we got a few inches of snow the night before the traps were to be collected.

Snow with some grass poking through and a blue flag in the middle.
Pitfall trap under snow. It is somewhere near the flag. 3/8/25.

Even though each trap was marked with a flag and had a big rock on top, some were hard to find under the snow, and I had to be careful to avoid spilling too much snow into the cups.

When I got them back to the lab, I was in for a surprise.

Ant with reddish head and thorax, brown abdomen, and long legs.
Ant caught in pitfall trap. Species unknown, but not Pogonomyrmex. 3/8/25.

The cups were not overflowing with life, but there was plenty to see. The most common insects were ants. About half (maybe 5) were the large, leggy species shown above. The rest were the much smaller species shown below. Sorry there’s no scale, but they were moving too quickly for that. I preserved some, so may post better photos later.

Small ant species. 3/8/25.

There were also quite a few springtails (Collembolans), probably of several species.

Tiny insect with long antennae.
Springtail caught in pitfall trap. 3/8/25.

They are extremely tiny, and I know little about them, so all I can say at this point is that there were springtails active in the neighborhood.

Brown spider with light markings on dusty background.
Spider from pitfall trap. 3/8/25.

There were also at least three spiders, of at least two species. According to iNaturalist, the spider shown above is a ground crab spider in the genus Xysticus.

Most exciting were two species of beetles.

Weevil on light background.
Grey weevil with dark blotches, covered with coarse hair. 3/8/25.

One weevil fell into a trap. It is about 6 mm from nose to tail. Looks somewhat like Ophryastes, but I am not certain.

Hairy, reddish beetle larva next to a millimeter ruler.
Beetle larva, probably in the family Melyridae. Note the relatively long thorax and the urogomphi (spiky things) extending from the end of the abdomen. Ruler scale is millimeters. 3/8/25.

There were also two larvae that looked like they were in the family Melyridae, or soft-winged flower beetles. They looked identical to each other, so maybe they are relatively common around here. The larval biology of most beetles, including the Melyridae, is not well documented, so it may be impossible to determine the species of these guys.

It was a pleasant surprise to find some little arthropods in the traps this month, especially a few species of beetles.

There were, however, no Tenebrionids as yet. In that way, this month’s collection does actually serve as a control. I expect that we may find some of them when the traps are reset in early April.

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