DESCRIPTION AND SEASONAL HISTORY. 23 



When the larva is fully grown, it ceases to feed and seeks out some 

 place in the crown of the plant among the litter and trash or on the 

 ground among similar material, where it spins a cocoon (fig. 6). 



COCOONING AND PUPATING. 



The cocoon is composed of fine white threads and the construction 

 by the apparently blind larva was in part observed by Mr. Ainslie, 

 who describes its movements as follows: A larva was seen moving 

 about in its snow-white, almost transparent, gauzy, unfinished cocoon. 

 It proved to be spinning a closer mesh from within. Instead of 

 spinning the silk from a gland that opened into its mouth, as was 

 supposed, the fluid from which the silk is made is taken into the mouth 

 apparently from a gland in the caudal segment. The larva applied 

 its mouth to an opening or gland close to the anus, appeared to move 

 its jaws slightly, and then, with a quick 

 movement of the body, was* straightened 

 out as much as possible in its confined space, 

 and instantly the head was applied to the 

 inner network of the cocoon. A slender 

 glistening thread was seen leaving the 

 mouth, being attached glutinously to each 

 thread that it crossed. The larva worked 

 rapidly and nervously, nearly always car- 

 rying its new thread in a rather straight 

 line. From 30 to 50 seconds were required 

 to discharge a single mouthful supplying 

 thread for one-third or one-half a revolution fig. g.— The alfalfa weevil: cocoon. 



inside the COCOOn. Much enIar S ed - (Author's illus- 



When all the supply was exhausted, the 

 head groped aimlessly about for a few seconds, then was applied to the 

 caudal gland as before. The body would then straighten with a quick 

 movement and almost instantly the thread would be again flowing as 

 before. The new thread was guided skillfully across the meshes, rarely 

 if ever following the line of a thread already laid. A very slight jar 

 would cause a sudden halt for perhaps half a minute, then the opera- 

 tion would hesitatingly proceed. As the irregularly oval cocoon is 

 too small in any diameter to allow the larva to straighten out, the 

 larva moved about by thrusting its small head into a mesh, swinging 

 the body into the desired position; the head would then be moved 

 to another mesh and the operation repeated. The fluidity and amount 

 of the silk must vary as spinning progresses, the silk becoming more 

 viscous or less copious as the cocoon approaches completion. 



The pupal period, according to Mr. Parks's notes, during the middle 

 of May lasts about 9 days, the larvae spinning their cocoons about 5 

 days before pupating. (A pupa is shown in fig. 7.) At the end 



