i 4 2 AMERICAN SPIDERS 



claws. Many are swift runners that can be seen dashing across paths 

 with the celerity of vagrants. Their habits are thoroughly interest- 

 ing, although they are not known to do things quite as amazing as 

 do some of the aerial web spinners. 



Three different families occur in American fauna, the Dictyni- 

 dae, Zoropsidae, and Oecobiidae; two other families of somewhat 

 greater interest are not found within our territory. One of these 

 latter, the Eresidae, is made up of robust, moderate to large crea- 

 tures, similar to jumping spiders, and often quite brightly colored, 

 especially the males. Some of them are fine tunnelers and are even 

 known to use a trap door to close their tubes. Many spin sheet 

 webs connected with tubular retreats. Some species of Stegodyphus 

 join together and spin an immense communal web over bushes, 

 forming an irregular saccular retreat partitioned in various ways, in 

 which many individuals live amicably together. 



The second exotic family is the Psechridae, whose only repre- 

 sentation in the New World is one small group from Mexico, 

 whereas several large conspicuous types are common in the Pacific 

 regions. These spiders will often spin a huge web, at the center of 

 which is a flat sheet similar to those made by the sheet-weaving 

 Linyphiidae. The spiders creep over the ventral surface of the sheet, 

 hanging back-downward, as do the aerial ecribellate spiders, on 

 greatly elongated legs of which the terminal segments are flexible. 

 One of the strange features of the psechrids is the presence of well- 

 developed claw tufts on the tarsi. These are probably used for a 

 very different purpose than are the claw tufts of the wandering 

 spiders. Perhaps they aid in unfastening the median claw, and serve 

 in the same way as the accessory claws of the orb weavers. 



Among the largest typical cribellate weavers of the American 

 Dictynidae are the ground spiders of the genus Amaurobius. Many 

 of the females are robust creatures attaining a length of three-fourths 

 of an inch. Their colors are usually brown or black, but the dorsum 

 of the abdomen is variegated, with a series of yellowish chevrons 

 forming a pale band. The males, not far inferior in size, are usually 

 in evidence only during the fall and very early spring, and are 

 rarely seen during the rest of the year. A single native species 

 Amaurobius bennettiis common in the eastern part of the United 

 States, but many others abound in the mountains of the western 

 states and in the northern woods. 



Amaurobius spins a large irregular web in dark, moist situations. 

 Whereas much of the silk may be hidden from sight, not infre- 



