METAZOA INSECTA. 469 



while the opposite end of the body is held in the loop of 

 a second Y-shaped thread (fig. 2). 



The adults (No. 1 197) have the robust body of moths. 

 The head is broad and the antennae are usually thread- 

 like but are enlarged near the end, though the tip curves 

 backward like a hook. The sucking tube in these insects 

 is remarkably long. 



Skippers fly by day ; a few hold their wings when at 

 rest in a horizontal position, while some hold the hind 

 wings in this way and the fore wings erect ; most, how- 

 ever, hold their wings erect like the butterflies next to be 

 described. 



Papilionidae or swallow-tails. This family includes the 

 more generalized butterflies. The caterpillars of the 

 swallow-tails (No. 1198, Papilio asterias, dorsal view; No. 

 1199, side view) are naked, being without spines or con- 

 spicuous hairs. They have two processes on the pro- 

 thorax called osmateria which can be thrown out and 

 withdrawn, and since they give out a disagreeable odor 

 are supposed to be organs of defence. 



The pupa (No. 1198), now called the chrysalis, is 

 angular and not rounded like that of the moth. It is 

 without a cocoon but is covered by the dry, hardened 

 skin of the larva ; it hangs suspended by the tail and a 

 loose girt around the middle. 



The adult (No. 1198) has a slender body very different 

 from that of the moth. The antennae are knobbed at 

 their ends without a recurved hook. The three pairs of 

 thoracic legs are well developed. These insects fly by day 

 and when at rest hold their wings erect. The Papilioni- 

 dae can be easily distinguished from other butterflies by 

 the prolongation of the hind wings. 



Pieridae. Our most common white and yellow butter- 

 flies belong to the Pieridae. The larva of the cabbage 

 butterfly, Pieris rapae Schrank (No. 1200 larva, chry- 

 salis, ; No. 1201, 9) is a naked green caterpillar. 

 The chrysalis is suspended in the same way as that of 



