352 
Journal of Agricultural Research 
Vol. IX, No. 10 
examined; but the minute entrance hole with a small amount of pellets of 
reddish frass and the empty shell of the egg are sure indications of infes¬ 
tation, and dissection of the boll will reveal the small larva mining within 
the wall. 
Infested bolls normally become more or less recognizable by discolora¬ 
tion of the .shell, which soon assumes a reddish or black color over the 
infestation; but as such discoloration may occur in uninfested bolls from 
other injury and does not always follow infestation of the pink bollworm, 
no conclusive discrimination between infested and uninfested bolls* can 
be made without the discovery of the eggshell and the entrance hole. 
There is considerable individual variation in the further course of the 
attack, partly depending upon the location of the egg and the condition 
of the boll and partly upon the direction the larva may happen to choose. 
Most commonly the larva bores in near the apex of the boll and tunnels 
down through the walls to the base before it attacks one of the lowest 
seeds. This it eats partially and then proceeds to the next seed above, 
ending as a full-grown larva in one of the seeds nearest the tip of the boll. 
Sometimes, however, the opposite movement takes place. A larva 
generally confines itself to a single section of the boll, but an adjoining 
section is often invaded, and sometimes all sections will be more or less 
attacked by a single larva. 
If a boll for any reason becomes unsuitable, the larva will readily leave 
it and migrate to another, into which it eats its way through the shell, 
making a large, conspicuous, frass-surrounded hole. 
The larva eats the seeds and tunnels and soils the lint, causing the arrest 
of the growth and the rotting or premature and imperfect opening of the 
boll. Not only the seeds and the lint actually attacked are lost, but the 
uninfested parts of the boll are retarded in growth and greatly depreciated 
in value by the attack of even a single larva. When, as is often the case, 
two, three, or more larvae infest a single boll, the value of the seeds and 
lint is entirely destroyed. 
The larva is exclusively an inside feeder within the boll and does not 
attack the leaves or shoots of cotton. Sometimes the young larvae may 
be found in the ovary of the flower, devouring the tender ovules and 
preventing the formation of the lint. Such larvae rarely attain their full 
growth in the flower, but migrate to a boll for their later support. Much 
more commonly, however, it is the larger, well-formed boll, which is 
attacked. 
There are four larval instars. The younger larvae are nearly pure 
white, with a brown head, thoracic shield, and tubercles. It is only in 
its last stage that the larva assumes the strong pink suffusion which 
has caused its popular name “pink bollworm. 1 
1 It should be noted that the larvse of many other Microlepidoptera assume a similar red or pinkish 
coloration at maturity and that the larva of Pyroderces rileyi, described in the latter part of this paper, 
which also occurs in cotton bolls, has a decided reddish color throughout its life. 
