PEOCEEDINGS OF THE NATIONAL. MUSEUM 



VOL. 75 



of four segments and maxillary palpi of six segments, and three 

 spines on the eighth sternite of the male indicate primitive condi- 

 tions in this group, then the first three genera included in the table 

 certainly belong together and are more closely related to one another 

 than to any other of the genera considered. The other genera have 

 become specialized along one or more of the three lines indicated 

 above, and by selecting one of these three lines of specialization on 

 which to base the main divisions we get a different grouping of 

 the genera from that which would have been obtained had we 

 selected either of the other two. It is my opinion that by making 

 the variation in the form and extent of the reduction of the anterior 

 ocellus the main point of departure the relationship existing among 

 the several genera can best be brought out when a simple linear 

 arrangement is employed. I have used such an arrangement in 

 the table submitted. 



