Introduction: What are Solifuges?
Members of the order Solifugae, usually referred to as solifuges, solifugids, solpugids or by an assortment of vernacular names (e.g., camel spiders, false spiders, haarskeerders, jagspinnekoppe, jerrymanders, roman spiders, sun spiders, walzenspinnen, wind scorpions), are a diverse and fascinating, yet poorly known, order of specialized, mostly nocturnal, cursorial hunting arachnids notable for their massively powerful two-segmented chelicerae, voracious appetite, and tremendous speed (Punzo, 1998). They constitute the sixth most diverse order of arachnids in number of families, genera, and species (Harvey, 2002). Many solifuges are able to run at extremely fast speeds (53 cm/sec) for short bursts, but like most arachnids, cannot sustain such rapid locomotion for long periods. Solifuges vary from a few millimeters to 10 centimeters in length and look superficially like stout, hairy, fast-running spiders with an extra pair of legs (leg-like, sensory pedipalps, held out in front of the body). They are, however, more closely related to members of the order Pseudoscorpiones (Kraus, 1976; van der Hammen, 1977; Grasshoff, 1978; Weygoldt and Paulus, 1979; Shultz, 1990; Wheeler, Cartwright, and Hayashi, 1993; Wheeler and Hayashi, 1998; Giribet and Ribera, 2000; Giribet, Edgecomb, Wheeler, and Babbitt, 2002; Coddington, Giribet, Harvey, Prendini, and Walter, 2004) than they are to spiders (order Araneae). The orders Solifugae and Pseudoscorpiones are placed together as the sole members of the superorder Haplocnemata (Shultz, 1990) within the class Arachnida. The order Solifugae is indisputably a monophyletic group (a group whose members share a common ancestor and which includes all descendants of that ancestor) based upon both morphological and molecular analyses (Wheeler, Cartwright, and Hayashi, 1993; Wheeler and Hayashi, 1998; Giribet and Ribera, 2000; Giribet, Edgecomb, Wheeler, and Babbitt, 2002). Besides their enormous chelicerae, autapomorphic characters (derived features shared uniquely by members of the group) include stalked, leaf-like chemosensory structures (malleoli or racquet organs) on the coxae and trochanters of the fourth pair of legs (Brownell and Farley, 1974), prosomal stigmata, peculiar cheliceral flagellae on males (Lamoral, 1974), palpal coxal gland orifices, palpal suctorial organs (Cushing, Brookhart, Kleebe, Zito, and Payne, 2005); opisthosomal ctenidia; and a monocondylar walking leg joint between the femur and patella (Shultz, 1989). Much of the systematics, morphology, behavior, and natural history of Solifugae remains unknown (Coddington, Giribet, Harvey, and Prendini, 2004; Harvey, 2002, 2003).
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