LEPIDOPTERA . 
367 
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 f . g . „*.- Mte atkymu, co/« g «i. 
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, Megathymns cofaqni (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'cai). 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 Hesperiidae, having a small head. This species is widely 
distributed through the southern part of our country. 
