tiny arachnids in the neighborhood

It’s mid-January, which means that bugs have been pretty low-key. They’re still out there, of course: on warm, sunny afternoons, the sulphurs and flies can be seen, flitting and buzzing about. Otherwise, invertebrates lay low during the colder months, and I do mean that literally. There’s a whole world beneath our feet and, specifically, beneath the rocks on the ground. Yesterday, I explored a bit of trail in our neighborhood that cuts through typical low Sonoran Desert. Unlike the terrain at the national park, this area was disturbed some time ago, when the housing development was put in in the 1980s and 1990s. Because of this, there are few to no saguaros to be seen. The cacti that dominate the landscape are mostly prickly pears, but there are also quite a few fishhook barrels and plenty of healthy-looking clumps of mammillaria cacti. Different herbs and shrubs can be found, including brittlebush, desert marigolds, fairy duster, chia, and so on. Also present are several species of trees — mesquite, acacia, buckthorn, and creosote being the most prominent. The point is, despite this area being all but bulldozed a handful of decades ago, the plant diversity is still pretty impressive.

This landscape is pretty typical for the outlying areas of Tucson, where housing developments have popped up in the last 30 or so years. The mammal, bird, and reptile diversity is all pretty impressive, and I do see quite a few arthropods around our house. But what about the tinier bugs? I’ve always found a good number of pseodoscorpions, spiders, and mites beneath the rocks at the national park and along Mount Lemmon Highway — would those same arthropods be present here, in the wilder suburbs of Tucson?

I decided to find out, and I wasn’t disappointed. Turning rocks yielded several pseudoscorpions, three different species of spiders, and a fancy-looking mite with legs so long it resembled a harvestman.

The three pseudoscorpions pictured above are likely all the same species, just instars of different ages. The second one was the smallest of the three, about the size of a sesame seed, and almost completely translucent. What always shocks me about these guys is how fast they are! Much like a fleeing crayfish, they scuttle backward at a rather alarming speed.

Likely Asagena fulva, female, from the family Theridiidae.
A crab spider, Xysticus sp., female.
Some sort of Gnaphosid.

The spiders weren’t keen on the sudden brightness, but they warmed up quickly in the sunlight. The air temperature was maybe only 60°F, but the sun made it feel significantly hotter!

The most interesting find, in my opinion, was this long-legged mite! It looked more like an Opiliones than a mite, and once in the sunlight, it was fast — making it very difficult to photograph. I don’t know what family this one is in, so any input is really appreciated. I just love the markings on its body, and the color of its legs!

Finding tiny arachnids like these is important, I think, especially in a developed area. The health of a location is really dependent on the smallest of creatures, so seeing all these pseudoscorpions, spiders, and mites is a good indication that the wilder areas of our neighborhood are doing okay. It goes without saying that all rocks were carefully replaced as they were found!

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