Dirk Stevenson (Altamaha Environmental Consulting)
Keep reading to join Dirk Stevenson on another journey to learn more about some of the lesser-known species sharing a habitat with gopher tortoises!
A few Novembers ago, Matt Moore and Ben Stegenga noticed a suspicious track at the mouth of a large gopher tortoise burrow. They were on the hunt for serpent commensals on a xeric sand ridge located on a protected tract in the Altamaha River drainage, Georgia. Using a burrow camera, they scoped the tunnel to find a good-sized eastern diamond-backed rattlesnake curled about eight feet from the entrance. The men admired the rattler, chuckling as it tongue-flicked the cylinder that housed the camera. As they packed to go, they noticed an odd invertebrate scurrying over the sugar sand of the burrow apron. Moore and Stegenga recognized the inch-long arachnid as a solpugid, even though neither had ever seen one in the wild before. Aware of their extraordinary find, they scratched their heads – solpugids were not known to occur in Georgia.
Solpugids are arachnids and members of the Order Solifugae. Known colloquially as wind scorpions (they can run fast as Forrest Gump – up to 10 mph) or camel spiders, many species are a luscious honey-yellow in color. The sixth most diverse order of arachnids, Solifugae includes 12 families and more than 1,000 living species. The largest solpugids, impressive by invertebrate standards, reach about five to six inches long with their legs fully extended. Adults of most species, however, are about an inch long. Hirsute bodies and conical heads ending in a pair of massive, vertically-oriented appendages called chelicerae lend solpugids a fierce and warthog-ish appearance. However, with the exception of a single species (Rhagodes nigricinctus, native to India) they lack venom glands and cannot inflict serious bites.
Solpugids have four pairs of legs, although it looks as if they have five. The anterior-most pair are actually elongate mouthparts called pedipalps. The pedipalps are richly-equipped with sensory hairs, and terminate in adhesive suctorial organs that aid in climbing and prey capture. (Yes, any specimen you place in a jar or similar container will immediately climb out!). Known for their voracity, solpugids are not bashful about taking on good-sized prey. They macerate and liquify prey using repeated grinding movements of their deeply-toothed chelicerae, which are capable of crunching through insect exoskeletons. Larger species are known to dine on scorpions, geckos, and shrews, and adult females will gorge themselves to the point where their mobility is compromised. Cannibalism is common. Foraging solpugids are search-and-find-it predators that run about erratically, their pedipalps extended well in front of the body, repeatedly tapping the substrate as they go.
Abundant in tropical and subtropical regions of Africa, Asia, and the Americas, most solpugid species are associated with deserts and other arid ecosystems. Nearly 200 species are known from mainland western North America, yet only a single species, Ammotrechella stimpsoni, is known east of the Mississippi River. Ammotrechella stimpsoni has been documented only from peninsular Florida (as far north as Clay County, where the late Alabama herpetologist Bob Mount collected one from a pocket gopher mound), the Florida Keys and the Dry Tortugas. Thus, the Georgia solpugid found by Matt and Ben appeared to represent not only the first record of a solpugid for Georgia, but also a significant range extension for A. stimpsoni. Or, possibly an undescribed species. I contracted a serious case of solpugid fever and joined Matt and Ben to initiate a study of the Georgia population.
First, we canvas all museum collections in search of other Georgia specimens that may have slipped through the cracks. A retired biology professor from Columbus State University mentioned that decades ago a colleague brought a solpugid into the lab that he reported had been found “in south Georgia”, but he can’t recall where. Then, bingo! We locate a single specimen at the University of Georgia Museum of Natural History. The accompanying locality data reads, “collected in 1973 at a hosiery factory in Macon, Georgia”.
This news is intriguing. Perhaps the specimen was transported there, but Macon sits slap on the Fall Line, home of deep sand deposits that date from the Cretaceous. In fact, the Fall Line sandhills, essentially ancient beaches and sandbars, are considered to be the oldest of all Coastal Plain environments. Could a novel solpugid have evolved here? I cold-call a county office and speak with a long-time Macon resident, Lynn. She tells me that Macon was a hotbed of textile factories back in the 1960s, but they have long closed or burned down. We discuss sandhill herps too. Lynn shares a cool story of a “spreadin’ adder” (Heterodon platyrhinos) she kept as a pet for 12 years; when toads were in short supply, her hognose would eat Alpo from a fork.
Subsequently, we locate a single Ammotrechella specimen in the invertebrate collection at Georgia Southern University, Statesboro, that had been collected at the same site where Matt and Ben observed their specimen. Apparently, a biology student collected the solpugid “inside Cabin 3”, during May 1991. At this juncture, a venerable invertebrate taxonomist, Dr. Lance Durden of Georgia Southern, joins our team.
The following summer, my wife and I pack up our terriers, grab fixin’s for a weenie roast, rouse Messrs. Moore and Stegenga, and head to Cabin 3. We search like earnest herpers, feverishly scratching litter and noodling about logs, but daytime sampling doesn’t disclose any solpugids. Peeking beneath the exfoliating bark of some lightning-killed longleaf snags does reveal numbers of bark scorpions (Centruroides hentzi), and the impressive red-black-and-white assassin bugs (Microtomus purcis) known to sometimes eat them.
That night, our flashlight beams fall on the pillowy mounds of tortoise burrows as we walk the sand ridge in the dark. Woody stems bearing the scarlet flowers of a gorgeous aromatic mint (Clinopodium coccineum) surround some of the burrow entrances. Then, scanning the bark of a giant pine we notice the hyperkinetic form of what appears to be a 10-legged insect. It vanishes… But on a nearby oak trunk we spot another – yes, it’s a solpugid! By midnight we have seen over a dozen, all on tree trunks. One is observed dining on a conspecific.
We continue solpugid surveys on humid nights over the next 16 months and make a number of interesting ecological observations. Disturbed individuals squeeze into cracks in the bark or drop to the ground where they remain immobile in the litter. We learn that this strongly arboreal species produces only one new generation per year. About the time most adults seem to disappear from the landscape in July, wee-teensy, 4 mm-long second instars (most solpugids molt 7-10 times before becoming adults) appear – we see them roaming tree trunks and dispatching tiny ants at this time. It is suspected that they emerge, then disperse, from nests made in shallow burrows in the sand.
Morphological and genetic analyses of the solpugids found at this south Georgia site indicate that they belong to an undescribed species, related to but notably different from A. stimpsoni, The new species is hairier than A. stimpsoni, has different cheliceral dentition in both sexes, and also differs in other morphological structures. Four genes sequenced from A. stimpsoni and the new species show interspecific differences. A manuscript describing the new species, authored by Lance Durden and colleagues, is in preparation.
“Here is an odd creature, a monstrous apparition. How weirdly fashioned, how ill-proportioned, how evil and forbidding in its hideous shape and coat of bristling hairs!”
From: Hingston, R.W.G. 1925, Nature at the Desert’s Edge (in reference to solpuigids)