508 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 9 



the posterior end of the chrysalHs. Just prior to pupation the color of the mature 

 larva undergoes a change from the olive-green of the active condition to a smoky- 

 drab which is apparently indicative of maturity. The third instar at El Centro 

 required during midsummer about 1.9 days for completion. 



The Pupa 



The pupal cocoon may be placed in one of several locations. It is 

 occasionally seen at some point on a leaf; it is often formed on the leaf 

 petioles; but most frequently it is placed at some point along the main 

 or lateral stems (see PI. 36, figs. 1 and 3). Just before making the 

 cocoon a series of stout, upright bristles is placed in a graceful ellipse 

 so as finally to surround the cocoon. These closely set stalks form a 

 stockade and are intended, probably, as a protection against preda- 

 tory species. 



Table II presents the data concerning the occurrence and distribu- 

 tion of the Bucculatrix pupae on 32 closely scrutinized plants. These 

 plants were pulled at random from a heavily infested field which aver- 

 aged 16 inches in height. The examination was made August 8, and 

 the results contained in the following table also afford a very good idea 

 of the degree of infestation at that time. 



In constructing the cocoon each end is woven to a point near the 

 middle, whereupon the larva withdraws into one half of the cocoon 

 and deftly spins a few tie-fibrils between the ends of the opposed flut- 

 ings; the gap is then entirely closed with a mesh of cross-fibrils. From 

 the pupal records of a large series of bred individuals we find that the 

 average duration of the pupal period for June and July at El Centro 

 is 5.7 days. The development of the cotton leaf-perforator may be 

 summarized, then, as follows: 



Days 



Egg stage 1 (plus) 



Leaf-mining stage 3 



First molt 1 



Second larval instai- 1.5 



Second molt 1.1 



Third larval instar 1.9 



Pupal period 5.7 



Total 15.2 



