HESPERIOIDEA OF AMERICA 107 



position between the sexes of several species. Larvae borers in 

 stems of plants. Fig. 31. 



Barnes and McDunnough's revision of this family is so satis- 

 factory that I am going into very little detail in 

 treating it. I have worked out the following key 

 to the North American species of Megathymus Fig. 31. Megathy- 



.,.,.„ ii .• i mvs streckeri Skin 



from the material in the Barnes collection, and ner . ciub of an- 

 believe that it will suffice for the determination of 

 most of the material likely to fall into the hands of collectors ; 

 those who are deeply interested in the family will doubtless ob- 

 tain the few articles which are useful to students who make these 

 insects a hobby. Only one genus is represented in our fauna. 



Genus MEGATHYMUS Scudder 

 Megathymus Scud., Syst. Rev. 62, (83), 1872. Type Eudamus 

 yuccae Boisd. & Lee. 

 Characters of the family. 



Key to the species 



1. Under surface with a large white patch contiguous to vein 8 of the 

 secondaries, or this spot the largest on the wing; no more than a trace 



of extra-median pale spots on secondaries yuccae 2 



Under surface of secondaries with a more or less complete transverse 

 row of pale spots and with larger spot on vein 8 outward 3 



2. Size large, 55 to 75 mm. Spots of upper surface bright yellow. Under 



surface of secondaries gray at margins yuccae 



Size smaller, seldom over 55 mm. Spots pale yellow. Outer margin 



of secondaries narrowly or not at all pale race coloradensis 



Size similar to coloradensis. Spots yellowish to white. Secondaries 

 with a broad pale outer border race navajo 



3. Size very large, 65 to 90 mm. Spots of primaries bright yellow. Sec- 

 ondaries without discal spots above and with at most a slender, linear 



pale margin ursus 



Size smaller, not over 70 mm. Secondaries with discal spots, a erenu- 

 late marginal band or with pale areas not bright yellow 4 



4. Under surface of secondaries smooth, powdered with blue-gray scales 



at outer margin cofaqui 



Under surface of shaggy appearance, washed with gray scales and hairs 

 over entire surface, sometimes most evidently between transverse row 

 of spots and outer margin 5 



5. Upper surface of primaries with a pale basal area contiguous to vein 

 1; spots yellow to yellowish-fulvous, or with a transverse sub-basal 



row of spots on the under surface of the secondaries 6 



This area seldom present, if so powdery and not contiguous to vein 1 



