PINK BOLLWORM OF COTTON IN MEXICO. 11 



completed in an average of 13.3 days in the summer larvae. The sec- 

 ond and third instars resemble the first in general appearance, and 

 it is usually in the fourth or last larval stage that the larvae change 

 to the characteristic pink color from which the name "pink boll- 

 worm" is derived. Sometimes the pink color appears in the third 

 instar, especially if development has been retarded in some way or 

 the larva has been exposed to the air. The coloring first appears as 

 transverse pink lines on the dorsal side of the segments and diffuses 

 and deepens till there is only a small whitish or flesh-colored line left 

 between the segments. The color seems to be more pronounced in 

 the larvae which reach maturity in the late summer or early autumn 

 and is a very deep pink or dull red. The head and thoracic shield 

 are reddish brown with dark-brown mandibles and anal plate. The 

 ventral side, legs, and prolegs are white to flesh colored, the legs and 

 prolegs with brownish claws and crotches. The full-grown larva is 

 cylindrical and measures about one-half inch in length. 



With the fourth stage the larva becomes very active again when 

 disturbed and conceals itself as quickly as possible. A cocoon is 

 spun attached to whatever object the larva is hiding in. The full- 

 grown larva is never content outside a cocoon after it leaves a boll or 

 seed. If it is taken from one cocoon it will immediately make another. 

 How many times this will be repeated was not determined, but a 

 perfectly healthy larva is rarely if ever found outside a cocoon, 

 except when crawling from place to place. 



The pupa is whitish, with faint markings of pink when first formed, 



turning to a mahogany brown as it dries and to a darker brown 



before emergence. It measures 8 to 10 mm. in length by 2.5 to 3 



mm. in width. The surface is covered with a fine velvety pubescence, 



the posterior end terminating in a short, stout, upwardly pointing, 



hooklike process. 



Pupation of Summer Larvae. 



When the summer larvae have completed their feeding, they cut 

 to the outside of the boll directly through the carpel wall from the 

 last seed attacked and drop to the ground for pupation. 



This exit hole through the carpel wall is usually round and clean 

 cut and can be easily recognized as having been cut from the inside 

 of the boll. Plate II, A, gives a comparison of the entrance hole into 

 the boll of the common bollworm, Chloridea obsoleta Fab., and the 

 exit hole of the pink bollworm. The entrance holes of the common 

 bollworm are larger, not so clean cut, and surrounded by a raised 

 margin. They are not likely to be confused once both have been seen. 



In the case of the summer larvae, the holes made in the green 

 cotton boll are always for the exit of the larvae, and not for the issuance 



