12 Farmers’ Bulletin 1262. 
formed in Texas and Louisiana from 1906 to 1911 was 6 per cent, 
which must represent about the average survival occurring in nature. 
From 1914 to 1920 a rather extensive series of cage experiments 
has been conducted by the Department of Agriculture at Tallulah, 
La., utilizing from 20,000 to 30,000 weevils each year. These have 
been placed in hibernation under a rather wide range of conditions, 
which probably represent a fair average of those found by the weevil 
in seeking hibernation quarters around the cotton field. The annual 
survival in these series has varied from 0.3 per cent to 5.9 per cent. 
Emergence from hibernation depends primarily upon temperature 
and rainfall in the spring, although some minor factors are concerned. 
In the southern portions of the cotton belt emergence usually begins 
from the first to the middle of March, but farther north it is some- 
what later than this. Naturally, the individuals under the heaviest 
protection are affected latest by the temperature. . The consequence 
is that emergence from hibernation is prolonged. It has been known 
to extend from the middle of March to the 28th of June, and in even 
more extreme cases from the middle of February to about the first of 
July. There is usually a comparatively short period during which 
the emergence is most rapid but this may be broken up into several 
such periods with intervals of slow emergence due to changes in 
weather conditions. 
HOW NATURE ASSISTS IN DESTROYING THE BOLL 
WEEVIL. 
Although the possible production of offspring in a single season by 
one pair of weevils has been estimated at 12,755,100, nature has pro- 
vided several means of preventing such excessive multiplication. The 
most conspicuous of these are heat and insects that prey upon the 
weevil. 
EFFECTS OF HEAT. 
When infested squares fall to the ground they may become so 
heated that the larve are killed in a few minutes. The insect in 
the larva stage can not leave the square, as it has no means of 
locomotion whatever. Where the infested squares are subjected 
to the unobstructed rays of the sun the mortality is very high. 
This explains the well-known fact that dry seasons are unfavorable 
to the weevil and indicates great difficulty in controlling the in- 
sects in regions where precipitation is heavy. Occasionally as many 
as 90 per cent of the immature weevils in cotton fields inspected have 
been found to have been destroyed through this agency. The extent 
of destruction holds a close relation to the amount of shade. When 
there is no shade practically all of the larve and pupe are killed 
outright. Some of the important means of control to be described 
later are based upon this consideration. (See p. 15.) 
