32 



WILLIAM T. M. FORBES 



which shows the usual segments, coxa, femur, tibia, and tarsus; but 

 all are very small, and the tarsus is composed of a single segment and 

 ends in a single claw. The abdomen is without true legs, but the third 

 to sixth and last segments bear membranous prolegs, which may have, 

 at the tip, a series of hooks, or crotchets. There are spiracles on the 

 eide of the first segment of the thorax and the first eight of the abdo- 

 men. In many caterpillars, especially aquatic forms, the last spiracle 

 lies on the dorsum and faces backward, as shown in the figure of Car- 

 posina (fig. 293). The body, as a rule, bears a regular arrangement 

 of seta? on each segment. These setae are designated by numbers, as 

 shown in the figures, and are known as primaries; when there are a 

 small number of additional setae, they are known as sub primaries (rigs. 

 434, 439) ; a large number, indefinite in position, are called secondaries 

 (fig. 405). In certain families, in place of single setae in the primary 

 positions, the tubercles from which the hairs arise are grouped in warts, 

 each bearing a tuft of setae (fig. 406). In this case the caterpillar is 

 spoken of as having tufted hair. 



The hooks on the prolegs also show a definite arrangement (figs. 25 

 to 28). If those of a series are all of the same length, or regularly 

 graded in length, they are called uniordinal; 

 when alternately of two lengths, biordinal; and 

 when of three lengths, triordinal. If there are 

 one or more rows of rudimentary hooks at the 

 base of the functional ones, the arrangement is 

 called multiserial. The series of hooks may be 

 arranged either in one or two transverse bands, 

 a longitudinal band, or an ellipse which is 

 usually broken at one or two points. In very 

 FIGS. 25-28. HOOKS OF rare cases, when there is a longitudinal band 

 PBOLEGS, TYPICAL AEEANGE- on the inner face of the proleg, there is a 

 M ENTS . . , weaker band, or some scattered hooks, on the 



25, umordmal, umsenal; ' . 



26, biordinal; 27, trior- outer face. Fracker calls this arrangement a 

 dinal; 28, multiserial pseudodrcle. 



Pupa 



The pupa, or chrysalis (fig. 29), also shows all the structures char- 

 acteristic of an insect. All the appendages, however, are folded back 

 on the body and may be soldered to it. The most conspicuous append- 

 ages are the wings, which lie on either side of the venter, at the front 

 end of the body. The hind wings are almost completely covered by the 

 fore wings, but a small portion of their posterior edges may show. On 

 the midventral line lies the tongue, and between the tongue and the 



