LEPIDOPTERA 595 



Figure 721 represents in natural size one of the larger of the American 

 species, but many exotic species are larger than this one. Our 

 smaller species have a wing-expanse of at least 2 5 mm. Our best- 

 known species are brown or ashy gray in color, with the wings marked 

 with silvery white spots. 



It is said that these moths fly near the earth, and only in the eve- 

 ning after sunset, hiding under some low plant, or clinging to the stalk 

 of an herb during the day. Some of them fly with extreme rapidity, 

 with an irregular mazy flight, and have, therefore, been named swifts 

 by collectors. So long as either or both of the two preceding families 

 are retained in the suborder Jugatae, the Hepialidse may be dis- 

 tinguished as the Macrojugatas. 



In the Hepialidas the posterior lobe of the fore wing is a slender, 

 finger-like organ, which is stiffened by a branch of the third anal vein, 

 and which projects beneath the costal margin of the hind wing. As 



Fig. 721. — Sthenopis pur purascens . 



the greater part of the inner margin of the fore wing overlaps the 

 hind wing, the hind wing is held between the two. This is the type 

 of posterior lobe of the fore wing to which the term jugum is ap- 

 plied. (Figs. 74 and 75.) 



The larvae are cruciform and furnished with sixteen legs; they 

 feed upon wood or bark, and are found at the roots or within the 

 stems of plants. They transform either in their burrows, or, in the 

 case of those that feed outside of roots, within loose cocoons. The 

 pupse have transverse rows of teeth on the abdominal segments; 

 these aid them in emerging from their burrows. 



This family is represented in our fauna by two genera, Hepialus 

 and Sthenopis. 



Hepialus. — This genus includes our smaller species, which range 

 in wing-expanse from 25 to 55 mm. In Hepialus the apices of the 

 fore wings are more rounded than in Sthenopis. Ten North American 

 species have been described. 



Sthenopis. — This genus includes our larger species. In these the 

 apices of the fore wings are more pointed than in Hepialus, and in 

 some species are subfalcate. Four species have been found in our 



