STATE HORTICULTXJKAL SOCIETY. 247 



wood, Curtis, Fitch and others. Dr. Fitch describes this operation fully, 

 as observed by him, as follows : 



The first act of the worm is to eat the shell of the egg from which it has been 

 hatched. It first gnaws an opening on one side from the top nearly to the base, and 

 then very slowly nibbles the sides of this opening and the base of the shell, until it is 

 so cleanly consumed that no indication of the spot where it was placed remains. In 

 the instance observed the worm was occupied five hours in eating its shell. When 

 this is accomplished it remains at rest for a few hours. 



His further observations in reference to the habits of the young 

 caterpillar are so clearly stated and so interesting that I make no apology 

 for introducing them here : 



Its second act is to weave a mat or carpet to give it a more secure foothold upon 

 the leaf. Applying its mouth to the surface of the leaf and moving it from side to side, 

 it spins therefrom a thread of silk of most extreme fineness, which it fastens to the 

 surface, crossing it in every direction, until it forms a thin film, which to the eye 

 appears like a small glossy spot very visible in a particular reflection of the light, 

 looking as though the leaf had been slightly touched with varnish. If nothing occurs 

 to drive it therefrom, this spot becomes its residence for a few days. And where- 

 ever it takes up its abode subsequently it constructs a similar mat, into the threads of 

 which it can catch the minute hooks of its feet, to render its standing more secure than 

 it is upon the naked surface of the leaves. 



It next begins to feed upon the leaf, some six or twelve hours after it has finished 

 eating the egg-shell. At some point slightly outside of the edge of the mat on which 

 it is standing it eats a round hole, the size of a small pin head, into which it gradually 

 sinks its head deeper and deeper, until it passes through the parenchyma of the leaf to 

 the skin of its upper surface. 



As yet it is so small that the eye only perceives it to be a minute cylinderical pale- 

 yellow worm, usually lying straight and motionless on the leaf. But as it feeds on the 

 green pulp of the leaf its body acquires a green color and slowly increases in size, 

 growing about one-thirtieth of an inch daily. 



Foreign authors state that in getting its growth this cabbage-worm molts or casts its 

 skin " several times." I can say with perfect confidence, it is only three times that it 

 molts. When it first comes from the shell it is extremely soft and its skin admits of 

 much distention before it constricts the worm to such a degree that it requires to throw 

 it off It is not till it has grown to double its first size, and is 0.12 to 0.15 long that it 

 casts off its skin the first time. It then feeds and grows till it has again doubled its size 

 and is 0.25 to 0.30 long, when it molts a second time. It again doubles its size and 

 becomes about 0.50 long, when it makes its third molt; and the skin which it then 

 acquires it retains till it reaches maturity, throwing it off only when changing into its 

 pupa form. This is the uniform habit of these worms, as I have observed in a number 

 of instances. The only aberations I have noticed in these moltings are, that one of 

 them is sometimes deferred till the worm is much larger ; yet this does not appear to 

 affect the other moltings of the same worm, for these occur as usual. Thus in one 

 instance the second molting did not take place until the worm was 0.38 long; yet the 

 third occurred when it was 0.53. In another instance the second molting took place 

 when the worm was 0.30 long; yet the third was deferred until it was 0.64. 



The almost uniform color is pale green ; the full grown larva is a little 

 over an inch in length and about one-sixth of an inch in diameter. Dr. 

 Fitch says they are quite uniformly an inch and one-tenth in length, but 

 as a general rule I have found them in Southern Illinois oftener nearly an 

 inch and one-fourth in length. The constrictions between the segments 

 are not very distinct, but the body appears rather to be divided into 



