Superfamily Argiopoidea 



Genus PHRUROLITHUS (Phru-rol'i-thus) 



The sternum is large and prolonged behind between the pos- 

 terior coxae; the anterior row of eyes is procurved; all of the tarsi 

 lack scopulae, but are furnished under the claws with very small 

 bundles of from six to ten spatulate hairs; the tibia and meta- 

 tarsus of the first two pairs of legs are armed, on the underside, 

 with a double row of strong spines. 



These are small spiders, varying from one twelfth to one 



fifth inch in length, which live under stones and among moss or 



short grass, and are very active. They are 



sometimes ornamented with bright markings 



and iridescent scales. 



Eight species have been described from 

 the United States; of these 

 several are common. The 



jg§s£S? 



Fig. 652. 



PHRUROLITHUS 



ALARIUS 



Fig. 653. 



EPIGYNUM OF PHRUROLITHUS 



ALARIUS 



Fig. 654. PALPUS 

 OF PHRUROLI- 

 THUS ALARIUS 



males of the different species can be separated by the variations 

 in form of the apophyses of the tibia of the palpus; the females, 

 by the form of the epigynum. The following is our most 

 common species. 



Phrurolithus alarms (P. a-Ia'ri-us). — The male measures 

 one eighth inch in length; the female, nearly one sixth. The 

 cephalothorax is light yellowish, with a narrow black marginal 

 line, and two light gray stripes. The abdomen is gray, with 

 several light transverse bands or chevrons, which vary in size 

 and shape; it is clothed with iridescent scales. The first and 



576 



