J 
BIOLOGY OF THE MEXICAN COTTON BOLL WEEVIL. 81 
TEMPERATURES FATAL TO THE IMMATURE STAGES OF THE BOLL WEEVIL 
Owing to the lack of proper soil thermometers, it was impossible 
to determine accurately the fatal temperatures for the immature 
stages of the weevil. The thermometers in use frequently recorded 
maximums of 115 to 125° I°., and under these maximum soil tem- 
peratures it seems safe to assume that not more than 10 per cent of 
the immature weevils will survive on Norfolk sandy soils such as 
occur at Madison, Fla. 
THE EFFECT OF TEMPERATURE ON THE LENGTH OF THE DEVELOPMENTAL 
PERIOD OF THE IMMATURE STAGES OF THE BOLL WEEVIL. 
Mean temperature and humidity either shorten or prolong the de- 
velopmental period of the immature weevil. The exact amount of 
humidity required for development under optimum conditions has 
never been determined. A mean temperature of 84° F. has been de- 
termined as the optimum temperature for,development of the im- 
mature weevil stages. Were it possible for the immature weevil to 
have the exact amount of humidity and a mean temperature of 84°. 
the developmental period of the immature stages would be approxi- 
mately 8 days. Temperature and humidity, however, are never just 
in the right proportion and so the period of development varies under 
different conditions. 
THE EFFECT OF TEMPERATURE ON THE LENGTH OF THE DEVELOPMENTAL 
PERIOD UNDER INSECTARY CONDITIONS. 
Under insectary conditions the development of the weevil has been 
shown to be approximately 14.3 days from egg to adult. This period 
of development is much shorter than the period under field condi- 
tions owing to the smaller variation in extremes of temperature. 
The mean temperature at Madison, Fla., under insectary conditions 
during the months of June, July, and August approximates 81° F. 
according to the United States Weather Bureau records. The aver- 
age mean temperature is lower by 3° than is required for the optimum 
developmental conditions. Therefore it is to be expected that the 
developmental period would be approximately 14 days under in- 
sectary conditions. 
THE EFFECT OF TEMPERATURE ON THE DEVELOPMENT OF THE IMMATURE 
STAGES OF THE WEEVIL UNDER FIELD CONDITIONS. 
Under field conditions the development of the immature weevil is 
considerably retarded and prolonged. It has been shown that the 
infested squares remain on the plants for approximately 11 days 
after egg puncture. For fully 8 days after egg puncture the sap 
continues to flow to the injured squares and keeps the temperature 
lower than is required for proper weevil development. At night the 
