232 AMERICAN SPIDERS 



processes so characteristic of higher spiders. The epigynum of the 

 female is likewise unspecialized, and the orifices that receive the 

 emboli are still hidden beneath the integument. As far as is known, 

 these spiders still use the primitive embrace of the tarantulas during 

 the pairing, and both palpi are inserted simultaneously into the 

 epigynum. 



One group of these primitive hunters includes the familiar 

 Ariadna and Dysdera, and is made up almost entirely of active 

 runners whose chelicerae are capable of separate movement. Pres- 

 ent near the base of the abdomen are four usually distinct spiracles, 

 the posterior pair opening into tracheal tubes. The unpaired claws 

 may or may not be present on the tarsi. Most of these spiders have 

 elongated bodies, with legs of moderate length. All four of the 

 commonly recognized families have representatives within the 

 United States, but few species can be mentioned. 



The only member of the family Dysderidae found within our 

 borders is the cosmopolitan Dysdera crocata, a half-inch long, 

 orange-brown species with a pale abdomen, probably introduced 

 into this country from the Mediterranean region, where many 

 genera and species occur. The American Dysdera is rarely found 

 in natural areas, preferring situations near buildings, where it hides 

 under stones, boards, and other litter. An oval cell of closely woven 

 silk serves as a retreat; within it are placed the eggs, minus a special 

 covering or egg sac. 



Quite similar in appearance to the dysderids are the Caponiidae. 

 This group is best represented in the Americas, particularly in the 

 Sonoran subregion of North America. All the respiratory spiracles 

 open into tracheal tubes, a condition paralleled only in some of the 

 aerial spiders. An interesting feature, previously noted, is the pos- 

 session in many species of only the anterior median pair of eyes. 

 These are quite large, and dark in color. (Transitional conditions 

 are found in a genus Nopsides, with four eyes, and in the African 

 Caponina, which has all eight eyes still present.) Several species of 

 these interesting two-eyed spiders occur in the United States, but 

 they are relatively rare and have been little studied. The genera in 

 our fauna (Qrthonops and Tarsonops) have translucent keels along 

 the ventral line of the metatarsi and rounded apophyses at the base, 

 but the use to which they put these curious features has not been 

 ascertained. 



The six-eyed vagrants of the family Oonopidae y most of them 

 less than one sixth of an inch long, live in leafmold or under stones, 



