HABITS OF YOUNG LARVAE. 



77 



found on larger leaves just below these. Yet I believe that the larvae 

 always feed a little before leaving the leaf on which they were born. 

 The young larva does not eat entirely through the leaf until it is nearly 

 two days old, and often not until the fourth day after it leaves the egg. 

 Thus the earliest indication of the presence of the worms is numerous, 

 small, semi-transparent spots upon the larger leaves. The smallest lar- 

 vae which I found eating through a leaf in the field measured from 

 five-sixteenths to three eighths inch in length (8 ram to 9.5 mm ). In con- 

 finement the newly -hatched larvae eat the upper surface or lower surface 

 of the leaf according as they happen to be on one side or the other but 

 do not perforate the leaf till two to four days old. The injury done to 

 the cotton during this early part of the life of the larvae is inconsiderable. 



The young larvae are extremely active. Their first and second pairs 

 of abdominal legs being functionless, they resemble in their mode of 

 locomotion the true measuring- worms (Geometridae) even more than do 

 the full-grown larvae. When disturbed they drop from their resting 

 place by means of a silken thread ; frequently they climb back again in 

 the way commonly employed by spinning caterpillars, which is to bend 

 the head down to one side, and catch hold of the thread with the anterior 

 pair of legs, then, supporting the body by these legs, seize the thread 

 again with the jaws at as high a point as possible ; this act is repeated 

 until the larva regains its place. It sometimes happens that a larva in 

 moving about encounters one of these silken threads extending from one 

 point of support to another ; in such a case the larva is able to walk 

 along this thread with its ordinary looping motion, as if walking along 

 the lower surface of a twig. The abdominal legs are obviously fitted for 

 clasping any small object; but it is not until we examine the thoracic 

 legs with a microscope 

 that we can see how well 

 adapted they, too, are for 

 this purpose. 



In Fig. 2, a represents 

 the terminal portion of the 

 leg of a young larva, and 

 5 and c represent the claws 

 of a full-grown larva. It 

 will be seen that in each 

 case there is a piece 

 shaped something like 

 the hoof of a horse, w h ich , 

 acting with the true claw, forms a very efficient clasping organ. 



FIG. 2. 



In the 



young larva there is a curious fan-shaped appendage (Fig. 2, a a) at- 

 tached near the base of the claw, the function of which we failed to dis- 

 cover. This appendage is present in the Mlgrown larva ; but here it 

 loses its peculiar form, becoming long and narrow. 



Observations made in the field during the month of August indicate 



