The Texas Arachno-Challenge II

Vinegaroon, Mastigoproctus gigantea. Photo by Cullen Hanks.
Vinegaroon, Mastigoproctus gigantea. Photo by Cullen Hanks.

Last week, we learned that all 11 of the world’s arachnid orders can be found without ever leaving the boundaries of Texas. We were introduced to several of the more common orders, but left off heading to the Trans-Pecos for some of the largest of Texas’ arachnids.

Most people that live in central and west Texas, are familiar with vinegaroons (Thelyphonida). Our one species, which also occurs in other southwestern states and large parts of Mexico, can grow over three inches in length with a formidable looking pair of pinchers (technically called chelicerae) and a whip-like tail. Generally harmless, they can pinch and excrete acetic acid (a major component of vinegar, hence the name). Vinegaroons burrow under rocks and are active at night.

Undetermined windscorpion. Photo by Cullen Hanks.
Undetermined windscorpion. Photo by Cullen Hanks.

While you’re out taking a night hike looking for vinegaroons, keep an eye out for what, at first glance, looks like a medium to large size spider, quickly scurrying about, searching for prey on open ground or under the desert bushes. On closer inspection, windscorpions (Solifugae), also known as camel spiders or sun spiders, can easily be distinguished from true spiders by their segmented abdomen, disconcertingly large, paired mandibles (again, chelicerae), and what appears to be five pairs of legs (the 5th pair are actually modified mouthparts called pedipalps). Windscorpions occur throughout most of the western United States.

phrynus_butler
Undetermined tailless whipscorpion. Photo by Jason Butler.

Less common in the U.S., our eighth order, (Amblypygi) can be very abundant in the tropics, but are rarely encountered in Florida and Southwestern states including Texas. Like a flat, segmented spider, tailless whipscorpions look formidable with huge mandibles and creepishly long legs (particularly the 2nd pair that are used like antennas). However, if you are lucky enough to find one, your biggest challenge will be snapping a picture before it scuttles off at rapid speed. The single species in Texas, Phyrnus operculatus, has been recorded from the Big Bend region and a few caves in the southwestern edge of the Edwards Plateaus. Look under tree bark (where you can find a tree) and under stones, particularly in areas with large boulders and extensive limestone exposures that provide crackes and crevices in which the quarter-sized tailless whipscoprion can hide.

Microwhipscorpion, Eukoenenia spelaea. Photo from Smrz, Kovac, Mikes, and Lukesova, 2013. doi: 10.1371/journal.pone.0075989.g001.
Microwhipscorpion, Eukoenenia spelaea. Photo from Smrž, Kováč, Mikeš, and Lukešová, 2013. doi: 10.1371/journal.pone.0075989.g001.

Perhaps the strangest of the arachnids, the microwhipscorpions (Palpigradi) are also rarely seen. In fact, of the 11 arachnid orders, this is the only one still on the bucket list for yours truly. In appearance, a microwhipscorpion looks a bit like a tiny, eyeless vinegaroon that has had its ‘tail’ replaced by… a pipe cleaner. Like I said, they’re strange.

In Texas, species have been described from northeast Texas, near the Red River and from Austin, Texas. Like the pseudoscorpions, these tiny animals, though visible with the naked eye, will probably require magnification to locate. They have been recorded from under stones, in association with silverfish. Though you may be able to locate one by visually searching, there are also numerous contraptions that you can build to extract tiny animals from soil samples (I’m busy building one now to check off that bucket list). Although microwhipscorpions probably occur through much of the U.S., there is very little data on these enigmatic creatures.

Our final two orders will require travel to the Lower Rio Grande Valley, and they’ll be your biggest challenges. But to find out what they are, you’ll have to wait until next week, for the Texas Arachno-Challenge III.

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