76 
eighth to one-half grown, or sometimes even much larger, so that a 
corresponding!}' large or small portion of the kernels beneath is 
consumed during later development. Experiments made in the labo- 
ratory show that a bollworm ma}' consume from 30 to 50 kernels of 
corn durino- its entire life. AUowino- 900 kernels to an averao-e ear. 
this would mean an injury of from 3 to 6 per cent. Often more than 
one larva may mature in a single ear, and again the silk may supply 
the greater part of the food. Taking into consideration, also, that the 
apical portion of the ear, which is least valuable, is the first destroyed, 
the injury to field corn will probably not often exceed the estimate 
given above, and will, of course, fall lower wheie the percentage of 
infestation is less than 100. Although the eggs are laid in the fresh 
silks, the larv» scarcely ever hatch in time to destroy the silks before 
pollination has occurred, so that the fertilization of the infested ear is 
not interfered with. 
DAMAGE TO COTTOX. 
The extent of the injury caused by a single larva to cotton bears 
directly on many questions of bollworm control, and has been investi- 
gated carefully by a series of experiments and observations made upon 
cotton growing in the laboratory garden at Paris. 
The first series relates to very young cotton, and was made during late 
May and early June. At this time the plants were from T inches to 1 foot 
high. On May 31 two quarter-grown lafv^ were placed on one of the 
largest plants and covered by a wire-screen cage. Both entered the 
soil to pupate on the 10th of June, leaving the plant almost completely 
defoliated, after the fashion in which the cotton caterpillar injures the 
plants later in the season. Although the plant was in bad condition 
when the larvfc left it, later in the summer it was practically as well 
developed as its fellows in the immediate vicinity. This and other 
plants similarly treated had not yet formed any squares. The other 
plants treated gave, on the whole, about the same results as the one 
described, thoug'h the average extent of injury wa.> somewhat less. 
A second and more important series of observations was made during 
the latter part of July and the first half of August. The plants exper- 
imented on were about two weeks earlier than the general planting, 
and hence were at that time in the same stage as the field crop during 
August, when the third generation of bollworms is most destructive: 
that is, when full of squares, flowers, and bolls. Six of the more com- 
plete records are given in the succeeding paragraphs: 
E'.cper'iment 1. — A newly hatched larva placed on a plant \L\ feet high 
July 13. By the 25th it had entered the soil, after destroying twelve 
squares, one one-fourth grown boll, and one flower. 
Krperiment 2. — Small larva placed on a plant 3 feet high on July 
15. It entered the soil on the 2Tth. after destroyiiig one square, one 
small boll, and two large bolls. 
