Solifugae - Anatomy

Anatomy

Solifugae are moderately small to large arachnids (a few millimeters to several centimeters in body length), with the larger species reaching 15 cm (6 in) in head-and-body length. Figures quoting implausible sizes for sensational effect are seldom useful because when they are not outright fictitious they usually include leg lengths in non-standard ways. In practice the respective lengths of the legs of various species differ drastically, so the resulting figures often are misleading. More practical measurements refer primarily to the body length, quoting leg lengths separately if at all. Even so, it remains difficult to get solidly supported data because very few sources quote anything better than anecdotal claims. One source suggests a body length of up to 7 cm (3 in) Another gives a figure of 10 cm (4 in). Even if one takes values such as 15 cm at face value, they are extremes. Most species are closer to 5 cm long, and some small species are under 1 cm in head-plus-body length when mature.

The body has two main parts (tagmata). The prosoma or cephalothorax is the anterior tagma, and the ten-segmented abdomen or opisthosoma is the posterior part. As shown in the illustrations, the Solifugid prosoma and opisthosoma are not separated by nearly as clear a constriction as occurs in "true" spiders, the order Araneae. The prosoma comprises the head, the mouthparts and the somites that bear the legs and the pedipalps. The alternative name "cephalothorax" reflects the fact that the prosoma includes the parts that in insects form the head plus the thorax. Though it is not split into two clear tagmata, the prosoma does have a large, relatively well-defined anterior carapace, bearing the animal's eyes and chelicerae, while a smaller posterior section bears the legs. Like pseudoscorpions and harvestmen, Solifugae lack book lungs, having instead a well-developed tracheal system that takes in air through three pairs of slits on the animal's underside.