THE CATERPILLAR. 301 



color, smooth throughout, with a sharp point at the outer 

 end; and at the basal third they have an inflated globule, 

 the diameter of which is three times as great as that of the 

 hair. The walls of this globule are delicate, and when the 

 insect is alive they are fully distended, probably with air or 

 gas ; but when dead they collapse more or less completely, 

 often causing the hair to be bent at this place. The first 

 and second rows of tubercles on each side have only hairs 

 of this kind on them. Similar hairs occur on the larva of 

 the nun moth {Lymantria monaclia) before the first molt, 

 and have been called aerostatic hairs by Wachtl and Kor- 

 nauth, and the globules serophores. These authors believe 

 that these inflated globules have the ieffect of small balloons, 

 and aid in transporting the young caterpillars to a consid- 

 erable distance when the wind blows. The other kind of 

 hairs (filiform hairs) (Plate 48, Fig. 9) arise from the two 

 lateral rows of protuberances, and are unusually long, some 

 of them being longer than the body of the caterpillar ; and 

 they have several longitudinal rows of minute barbs extend- 

 ing the entire length. 



Later the caterpillar changes color, the tubercles becoming 

 black, the body reddish-brown with a row of dull reddish 

 spots along the middle of the back, one each on the fifth 

 to the eleventh segments inclusive. There are no retractile 

 tubercles in this stage. 



The time between hatching and the first molt, of twelve 

 caterpillars bred in confinement, in an unheated room, was 

 from eight to twelve days, the average being nine and one- 

 fourth days. The temperature very materially aflTects the 

 time before molting, for, when caterpillars were kept in 

 breeding cages near warm steam pipes, they molted in five 

 days ; while others, from the same egg-cluster, kept in a 

 cool part of the room, molted in seven days. 



Second Larval Stage. — Length, 7 mm. (about twenty- 

 seven hundredths of an inch), and the head is 1 mm. (about 

 thirty-nine thousandths of an inch) in width, shining black, 

 with numerous fine, pale-yellow hairs scattered over the sur- 

 face. Body, dark brown, with the tubercles black, and a 

 somewhat triangular yellowish spot on the top of segments 

 nine, ten and eleven, in the middle of which, on segments ten 



