OF WASHINGTON. 423 



trimacula are lighter, almost flesh colored on the disk. However, 

 it will be seen that the ranges in size almost overlap, while the 

 color of the hind wings varies, and in the female the specific 

 difference is very slight, sometimes barely appreciable, though I 

 believe that it always does exist to some degree. Since the 

 characters separating two well marked (as shown by the larvas) 

 species are so slight, it is necessary practically to place but little 

 dependence on color and markings in this genus and rely on 

 more subtle characters. For this purpose the male genitalia 

 prove of value. 



Unfortunately, a considerable number of species have been de 

 scribed and all without any reference to the genitalia. Not infre 

 quently the descriptions have been made from a single female 

 specimen. These it will not only be impossible to refer correctly 

 from the lack of a male, even on examining the type, but the 

 markings, as to what little they show, are always less definitive in 

 the female. 



Five species are represented in the collection of the National 

 Museum. They separate on genitalic characters as follows : 



Lower unpaired piece smooth. 



This piece symmetrical and flat, strap-shaped) the edges little 



raised fusca. 



This piece asymmetrical, tipped to the right concave modesta. 



Lower unpaired piece with angles or spines. , 



This piece with an angle above on each side, that on the left the 



larger stimulea. 



This piece with a thorn-like point on the tip below and on the left 



side extensa. 



This piece with a single spine below at tip, projecting toward the 



left side , apicalis. 



The male genitalia in this genus consist of a supra-anal plate, 

 flattened, somewhat concave below, the tip rounded but pro 

 duced in a sharp spine that is bent down at right angles ; below is 

 a long, horn-like prominence, more or less grooved above, diverg 

 ing from the plate at a slight angle. The side pieces are simple, 

 tapering, rounded, bending inward at the ends, not strongly 

 chitinized. Beneath is a well-chitinized strap-shaped or tubular 

 piece, or penial support, smooth, or with prominences, and usually 

 markedly asymmetrical, being turned with its lower aspect some 

 what to the left. 



The supra-anal plate differs slightly in trie several species. I 

 presume that specific characters could be tortured out of it; but 

 they would not be practically valuable. The side pieces are so 

 nearly membranous that their form is not well fixed and is at 

 best a very simple one. The lower piece, however, presents 



