6 H. C. FALL. 



Clypeal angles more distinctly defined — ambigua. 



Abdomen flattened and usually more hairy — brevidens, il- 

 lustris, thoracica. 



Basal joint of anterior tarsus stouter — knausii. 



Femora and tibia? (in part) more hairy within — brevidens, 

 illustris. 



Tarsi more densely pubescent — ambigua, pubipes, thoracica 

 dubia. 



Claws longer or differently toothed — schaefferi, anxius, plani- 

 dens (probably). There is a slight tendency for the claws 

 to be a little stouter in the females generally. 



The male genitalia are quite simple so far as examined, 

 while in the female they are entirely membranous and there- 

 fore useless for comparison. I have therefore not attempted 

 systematic dissection, but leave this phase of the subject for 

 the student who has the material and the time for its inves- 

 tigation. 



The genus is very widely dispersed in North America, and 

 occurs in every part of our territory; it reaches its maximum 

 development, however, in the warmer and dryer regions of 

 the Sonoran province. Of the 95 species recognized in the 

 present paper, 50 occur in New Mexico and Arizona, while 

 Arizona alone possesses 38. Three species only — tristis, 

 sordida and liberta — are known from Quebec and Ontario, 

 while from western British America there are but four thus 

 far recorded, viz. : brevicollis, obscura, residua and subangulata. 

 All of these are Rocky Mountain species, and with the ex- 

 ception of obscura, none of them has been found at any 

 considerable distance from our northern boundary. Obscura 

 has been collected by Mr. Frederick Knab in the Saskat- 

 chewan region, and the types of tristis were taken in lati- 

 tude 54°. 



Coming to our own territory, it will be interesting to present 

 in list form the species occurring in a considerable number of 

 States. These lists will not only be useful to the student of 

 distribution, but will also show at a glance the species which 

 the collector may expect to find in any given locality. Starred 

 species are known only from the region indicated. 



