32 IOWA STUDIES IN NATURAL HISTORY 



anal angle sometimes very slightly prominent. Costal fold pres- 

 ent in pylades and drusius but not in the other species. Fig. 10. 

 In establishing Cocceius Godman and Salvin state that it dif- 

 fers from Thorybes in the presence of the costal fold and that 

 this indicates that its relationship is rather with Achalarus. It 

 is related in many more points, however, to Thorybes, and the 

 costal fold does not seem adequate to separate the two groups as 

 genera. The male gentalia of the species are similar. 



Key to the species 



1. Fringes of secondaries white, at least in middle of outer margin . drusius 

 Fringes not white 2 



2. Under surface of secondaries transversely strigate 3 



Under surface not strigate 4 



3. Hyaline spots moderate to small, without dark outlines; ground color 



dark mexicanus 



Hyaline spots large with dark outlines ; ground color pale 



mexicanus, race nevada 



4. Spots usually large, extending from vein to vein ; palpi usually pale 



below bathyllus 



Spots usually small; palpi usually concolorous with body below, .pylades 

 Spots absent pylades, ab. immaculata 



1. THORYBES DRUSIUS 



Eudamus drusius Edw., Can. Ent. xv, 211, 1883. 



Biol. Cent.-Am., Rhop. II, 336, 1894. 



Skinner, Trans. Am. Ent. Soc. xxxvn, 185, pi. x, 1911. 



Arizona, June, July and August. Western Nebraska, Leussler. 



2. THORYBES PYLADES 



Eudamus bathyllus Harris (not A. & S.), Ins. Inj. Veg. 3rd ed., 312, 1862. 

 Eudamus pylades Scud., Proc. Bost. Soc. Nat. Hist, xni, 207, 1870. 

 Biol. Cent.-Am., Rhop. n, 336, pi. 80, f. 23, 1894. 

 Holland, Butterfly Book 324, pi. xlviii, f. 6, 1898. 

 Skinner, Trans. Am. Ent. Soc. xxxvn, 176, 1911. 



Occurs throughout the United States and most of Canada. In Florida 

 and Texas it has been taken as early as April and as late as October; far- 

 ther north it flies from May to August. 



ab. IMMACULATA 



Eudamus pylades immaculata Skinner, Trans. Am. Ent. Soc. xxxvn, 177, 

 1911. 

 This is a rather uncommon form in which the hyaline spots of the pri- 

 maries are entirely absent. 



