LEPIDOPTERA. 



367 



FIG. 448. Megathymus cofaqui. 



veins have split apart, so that they overlie the hind wings 



to a greater extent than they do in the female (Fig. 447), 



which probably represents a more primitive condition. It 



is a common occurrence for the wings of the male to be more 



highly specialized than those of the female, for, in the seeking 



of mates, the males 



fly more than do 



the females. But it 



is unusual for veins to 



coalesce to a smaller 



extent in specialized 



forms than in those 



more generalized. 



In other words, the 



ordinary course of 



specialization is for 



veins to grow together instead of to split apart. 



This family is represented in the United States by a 

 single genus, of which only three species are known. The 

 female of one of these, Megathymus cofaqui (Meg-a-thy'mus 

 cof-a-qui'), is represented by Figure 448. The male differs 

 in the smaller size of the spots on the fore wing, in lacking 

 the band of spots on the hind wing, and in having the upper 

 surface of the hind wing nearly covered with long fine black 

 hairs, which stand nearly erect. This species has been found 

 in Florida and Colorado. 



A much better known species is the Yucca-borer, Mega- 

 thymus yucca (M. yuc'cae). The female of this species differs 

 from that of the preceding in having much darker wings, 

 all of the spots being smaller, and in having only one or 

 two white spots on the lower surface of the hind wings. 

 The male lacks the erect hairs on the hind wings. The 

 larva bores in the stem and root of the Yucca or Spanish 

 Bayonet. It differs greatly in appearance from the larvae of 

 the HesperiidiE, having a small head. This species is widely 

 distributed through the southern part of our country. 



