129 



TouRN.\L New York Entomological Society, [Voi. xxl 



of antennae; presence and size of the vibrissse; and the shape, size and 

 color of the palpi, are characters of importance. In the thorax and 

 wings few specific variations occur in North American species, at 

 least of a tangible kind. The legs are quite rich in characters when 

 closely studied; three of the species show secondary sexual characters 

 here, only one of which was known heretofore. The length of the 

 hind tarsi of the males in comparison with their tibise is generally 

 important, and the number and arrangement of the spines on the under 

 side of the hind femora are very useful. The abdomen differs in 

 form from cylindrical to depressed, and is variously marked with gray 

 or white pollen. I have made no particular use of the hypopygium, 

 although I do not doubt that it has a variety of forms quite distinc- 

 tive when it is extirpated so as to be available for study, in the method 

 of Schnabl and Dziedzicki. 



The following table summarizes the data I collected from measure- 

 ments of the species. The columns contain the following data : 



Column I, the quotient obtained by dividing the entire horizontal 

 transverse diameter of the head by the distance separating the eyes 

 at the point of greatest approximation (about the level of the anten- 

 nae), in the male sex. 



Column 2, the same for the female sex. 



Column 3, the quotient obtained by dividing the length of the hind 

 tibia by the length of the hind tarsus, in the male sex. 



Species 



albitarsis 



antennata 



brevipes 



johnsoni 



nasoni 



palposa 



patellaia 



polita 



salina 



spinipes 



sociahilis 



sordida 



tentnculata 



ulizinosa 



^ The only male of johnsoni is teneral, the head somewhat shrunken, and 

 this number is undoubtedly too large. 



