THE HUNTING SPIDERS 223 



tinency of the appellation. For the most part, they have short, wide, 

 considerably flattened bodies, and some of the legs are extended 

 laterally at nearly right angles to the body. Those that most nearly 

 resemble true crabs are various ambushing species with short, thick 

 legs, the first two pairs of which are held sidewise and twisted 

 somewhat off the normal axis so that the lateral surfaces become 

 nearly dorsal in position. The laterigrade spiders were derived 

 from typical hunters with normal prograde locomotion, and they 

 exhibit various degrees of development between extreme variation 

 and near normality. The laterigrade form and attitude appear 

 sporadically among other families of spiders, but those discussed in 

 this section form a single line. 



The crab spiders wander about freely on the ground and on 

 plants, and have come to rely almost entirely on strategy and the 

 chase to capture insects. They spin no capturing webs; they ordi- 

 narily settle down in one place only at the egg-laying period, when 

 they produce large, lenticular egg bags hidden and guarded for long 

 periods by the mother. Their flattened bodies fit them eminently 

 for life in narrow crevices, under bark, or in debris, but many of 

 them lie appressed to the surface of plants or on rocks or soil in the 

 open. Some come out from their hiding places only at night, but 

 others seem to be committed largely to the capture of day-flying 

 insects. Their reliance on touch rather than sight would appear to 

 make them equally expert hunters by night or by day, and many 

 hunt at either time. 



The great size of the laterigrade spiders of the families Hetero- 

 podidae and Selenopidae (as compared with the relatively small 

 typical crab spiders) has occasioned their title of "giant crab 

 spiders." Only a dozen species of this tropical group are found 

 within the borders of the United States, these limited largely to our 

 southwestern states and to Florida. All are half an inch or more in 

 body size and have long legs of nearly equal length. 



Amazing for their celerity are the extremely flat species of 

 SelenopSy which, closely pressed against rock surfaces in their south- 

 ern Arizona canyon habitats, easily elude capture by whisking like 

 a squirrel into narrow crevices. Somewhat less speedy are the 

 plumper species of Olios, usually tawny or brownish in color, often 

 discovered with their bulky egg sac. They retreat into the spiny 

 security of prickly pear or cholla cacti. One of the largest, Olios 

 fasciculatus (Plate XXIX), achieved a sudden newspaper fame as 

 the "barking spider," and this despite the fact that it is mute and 

 not provided with sound-making organs of any kind. 



