LEPIDOPTERA OF NEW YORK AND NEIGHBORING STATES 31 



ture is shown in the figure of Eriocrania (fig. 38). The Hepialidae 

 have nine segments, but the structure is complex and not fully under- 

 stood. 



Larva 



The caterpillars show the same essential structures and appendages 

 as do the imagoes, but they are very different in development. As a 

 rule, only the head is chitinized, the skin of the body being thin and 

 flexible. The major part of the head (fig. 23) is composed of a pair 

 of sclerites, the epicrania. Between these, on the face, lies the front, 

 which is in most instances triangular and rarely reaches the top of 

 the head. Between the front and epicrania there are two very narrow 

 sclerites, the adfrontals, in some works called the paraclypeals. Below 

 the front is a third narrow sclerite, the clypeus. The lower half of 

 this, more or less, is composed of membrane. On the under side of 

 the head there are two small triangular sclerites, the postgenw. 



The antenna are very short and small, and lie immediately above 

 the mandibles, which are the principal structures associated with the 

 mouth. In front of the mandibles there is a flap, the lab rum (fig. 24), 

 which serves as an upper lip. Behind the mandibles there is a second, 

 somewhat thicker flap which functions as 

 a lower lip. It is composed of the fused 

 maxillae, and labium. It is complex in 

 structure and but little used in classifica- 

 tion. The eyes are represented by six 

 small, separate ommatidia, located in a 

 group low down on the side of the head, 

 as shown in figure 232. There are a con- 

 siderable number of setce which are con- FIG. 24. LABKUM, THE SET.E 

 stant in number and position in any given NUMBEEED ACCORDING TO FOBBES'S 

 species. A typical arrangement of these (") AHD HEINRICH'S 



T n r\c\ mi "* QlliiM { L,Cjt! 1 I 



is shown in figure 23. There are two T , , , , , ., __ 



n T ,1 mi *t* 1*2. L 3 , lateral setae; M,, M. 2 , 



methods of designating the setae. Tnejj^ me dian setse 

 right side of the figure is labeled accord- 

 ing to the method most often used in the past, while the left side 

 bears the system recently proposed by Heinrich. 



The body is composed of thirteen distinct segments, three belonging 

 to the thorax, and ten to the abdomen. The ninth segment of the abdo- 

 men is, in most cases, much smaller than the others. The prothorax 

 bears a sclerite on its dorsal surface known as the cervical shield (shown 

 in the diagrams at the head of each family). The setae on the side 

 are arranged in two groups, called the prespiracular, and the sub- 

 ventral, warts. Each of the segments of the thorax bears a small leg 



