250 



THE STUDY OF INSECTS 



The family includes our largest lepidopterous insects and all of our 

 species are above medium size. 



The wings are often furnished with transparent, window-like spots. 

 The frenulum is completely lost. The humeral angle of the hind wings is 

 largely developed, and is usually strengthened by a deep furrow. 



The larvae of most of our species live exposed on the leaves of trees 

 and shrubs; but some of them, as the New Mexico range-caterpillar, feed 

 on grass. They are more or less armed with tubercles and spines and are 

 very conspicuous on account of their large size. Most of them transform 

 within silken cocoons, which are usually very dense, and in some cases 

 have been utilized by man. These cocoons are often attached to trees 

 and shrubs, and are sometimes inclosed in a leaf. They can be easily 

 collected during the winter months, and the adults bred from them. The 

 larvae of some members of the family as Hemileuca maia enter the ground 

 to transform. 



The maia-moth, Hemileuca maia. — 



The genus Hemileuca is represented in 



our fauna by eleven species, but only 



two of these are found in the East. In 



maia (Fig. 438) the wings are thinly 



scaled, sometimes semi-transparent ; 



they are black with a common white 



band near their middle; and the discal 



veins are usually white and broadly 



bordered with black. There are great 



variations in the width of the white 



ig. 438.— cmiewa band on the wings. The larva feeds on 



the leaves of oak; it is brownish-black, with a lateral yellow stripe; and 



is armed on each segment with large, branching, venomous spines. The 



larva almost always enters the ground to transform. 



The New Mexico range-caterpillar, Hemileuca olivice. — Of the ten 

 western species of Hemileuca this is doubtless of the greatest economic 

 importance It is a grass-feeding species, which has been very destruc- 

 tive in certain sections of the cattle-range in northeastern New Mexico. 

 It was estimated that in 1809 the total infested area was at least 15,000 

 square miles, and that there were an average of 10 caterpillars to the 

 square rod over this region. For a full account see U. S. Dept. Agr. 

 Bull. No. 85, Part V. 



The io-moth, Au- 

 tomeris io. — This is a 

 common species in the 

 East. The female is 

 represented by Figure 

 439. In this sex the 

 ground-color of the fore 

 wings is purplish-red. 

 The male differs from 

 the female in being 

 somewhat smaller and 

 of a deeper yellow color, 

 but otherwise it resem- 

 bles the female. fig. 439.— Automerk io. 



