204 AMERICAN SPIDERS 



but without benefit of the specific modifications that the latter 

 enjoy. Only in the "earth wolves" of the genus Geolycosa do we 

 find features that suggest a first step toward true adaptation to a 

 subterranean life. Many wolf burrowers have thick, round bodies 

 and modified appendages, but in Geolycosa the cephalothorax is 

 higher and more strongly arched than usual, and the chelicerae are 

 unusually robust. The front legs are very stout and proportionately 

 thicker in both sexes, and all the legs lack prominent dorsal spines. 

 The earth wolves are confirmed exponents of a subsurface existence, 

 and spend almost all their lives within the burrow. Extremely shy, 

 they are reluctant to move very far from the opening even when 

 capturing insects, and usually sit partially inside, ready to retreat 

 at the slightest disturbance. Most other wolf spiders will wander a 

 few feet from the opening to wait for prey, or even forage long 

 and far from their tunnel retreat. These may be approached at 

 night with a lamp and easily captured, but the nervous earth wolves 

 must be dug out of the soil. 



The species of Geolycosa (Plates 25 and 26) are to be found 

 over most of the United States and temperate Mexico. Some are 

 yellow-brown spiders clothed with whitish hairs, but most have 

 dark red and brown bodies, masked by a covering of slate-gray or 

 brown hairs. The undersides of body and legs are usually marked 

 with jet-black bands and spots. They dig their burrows from six 

 to twelve inches into the ground the depth being somewhat de- 

 pendent on the character of the soil and line the whole with silk. 

 Ordinarily the tunnel goes almost straight down, and is enlarged 

 in the middle portion or at the bottom. 



Some of the palest American earth wolves (such as <wrighti 

 and pikei) live in the open sand of beaches and inland dunes, while 

 the darkest species, rafaelana, digs in the red, sandy soil of our 

 southwestern deserts. Those that live on bare surfaces ring their 

 burrow openings with an inconspicuous collar of coarse sand grains 

 glued together with silk. Still other earth wolves (miss our iensis and 

 turricola) are found in the plains or on hillsides where there are 

 numerous small objects suitable for use in turret-building. These 

 spiders almost invariably erect a prominent lookout from whatever 

 materials are close at hand, fitting the pieces together with metic- 

 ulous care by bending pliable straws and pine needles to the shape 

 required. The turret, which has been likened to an old-fashioned 

 log cabin chimney, is bound together with silk and has a smooth 

 inner lining continuous with the silk of the burrow. Some are 



