For the last two weeks, we have been working through the world’s 11 orders of living arachnids, all of which occur in Texas, the only U.S. state with such arachnid diversity. From common garden spiders to enigmatic microwhipscorpions, we’ve seen that these arachnids have a variety of unusual forms. However, we have to yet to be introduced to two of Texas’ most elusive arachnid orders, found in the Lower Rio Grande Valley.
The short-tailed whipscorpions (Schizomida) appear similar to vinegaroons and micro-whipscorpions, but lack a long “tail” or a “pipe cleaner”. These ant-sized arachnids are typically found, like micro-whipscorpions, in leaf litter or under rocks and logs. Aside from a single record of an undescribed species in Val Verde County, Texas short-tailed whipscorpions have only been recorded from near Edinburg and Rio Grande City. Most short-tailed whipscorpions are found in tropical regions around the world, and a few scattered records exist from southern states and as far north as Sequoia National Park in California.
So far, we’ve covered 10 orders, which means that we’ve come to the end at last. So what’s our 11th and final order that sets Texas apart from all other states? The hooded tick spiders (Ricinulei) are the smallest order of arachnids and they look a bit like a fuzzy tick with no head. Of course, they do have a head, but the mouthparts are hidden by a strange plate that hangs down where you would expect a face (hence the name ‘hooded’). Like its cousins, the hooded tick spider is found in leaf litter and soil and under rocks and wood.
Because these strange animals are primarily tropical, you might expect the U.S. to be out of luck for hooded tick spiders. But wait! In 1939 a single species was described from Edinburg, Texas, representing the only hooded tick spider known from the United States. But don’t think that finding one is as easy as a trip to Edinburg. “The curious, enigmatic arachnids of the Order Ricinulei are regarded as the rarest of all arthropods.” So begins the description of our Texas species, which also happens to be one of the smallest, at about 1/8 inch in length. Not only are these creatures rare, the original sampling location for Texas’ hooded tick spider, Pseudocellus dorothae, has been destroyed by urban development, and to my knowledge, the species hasn’t been seen since, meaning that if you find one, you’ll be the first person to do so in three-quarters of a century (if you see one, take a picture and please let us know!).
And with the hooded tick spider, the Texas Arachno-Challenge comes to an end. It will take you from woodlands of east Texas to the semi-tropical Lower Rio Grande Valley and west to the deserts of the Trans-Pecos. You’ll see tiny pseudoscoropions and giant vinegaroons, and if you succeed, you’ll be a true explorer of Texas biodiversity.