The weevil develops more rapidly in squares than in bolls and more rapidly 

 in small bolls than in large ones. Squares are the only food available in the early 

 part of the reproduction season, and they are far more abundant than bolls for at 

 least 60 days after fruiting begins. Bolls, however, carry the immature weevils 

 through unfavorable seasons because of their retarding effect on development and 

 their resistance to unfavorable temperature and humidity. When climatic condi- 

 tions are unfavorable to the weevils, the proportion of bolls to squares tends to 

 be greater than under favorable conditions. 



At present it is not possible to predict from weather records, with any cer- 

 tainty, increase of weevils, largely owing to variations in the characters of the 

 plants themselves. Both air and soil temperature and relative humidity are modi- 

 fied by shade, and this becomes increasingly important as the season advances. 

 Drought is the most important factor in checking weevil outbreaks, excessively 

 high summer temperatures and poor development of squares being associated 

 with it. 



1936 - Smith, G. L., and M. T. Young. Field movement of boll weevils in relation to 

 initial infestation and rainfall. J. Econ. Ent. 29(6): 1 063- 1 066. 



The numbers of boll weevils taken on adhesive screens in 9 cotton fields in 

 northeastern Louisiana during 1933, 1934, and 1935 were positively correlated 

 with the total rainfall during June, July, and August and with the number of days 

 with 0.3 in. or more rainfall during those months. In each year, there was a high 

 and fairly uniform infestation by overwintered weevils during May and early in 

 June. Infestation was higher in 1934 than in 1933 or 1935. The catch of weevils on 

 screens in June 1933, 1934, and 1935 was 64, 10Z, and 27, respectively. In June, 

 July, and August of 1933, 1934, and 1935, the total rainfall was 18.46, 11.23, and 

 6.89 in. Three-tenth of an inch of rain or more fell on 14, 9, and 5 days, respec- 

 tively. 



The catch of weevils on screens from June to November was 5,232 in 1933, 

 2,573 in 1934, and 369 in 1935. This decrease is shown graphically to be almost 

 directly proportionate to the decrease in the number of days on which rainfall was 

 0.3 in. or over, and to bear nearly as a direct relation to the total rainfall during 

 the 3 months. Of the total rainfall and days with 0.3 in. or more during June, July, 

 and August, more than 50% occurred in July in 1933, and in June 1934 and 1935. 

 The number of weevils caught in September 1933 was higher than in August of the 

 same year, but in 1934 and 1935 the catches for September were much lower than 

 in August. Heavy catches in November 1933, October and November 1934, and 

 October 1935 were due to the flights of the weevils seeking hibernation quarters, 

 which occurred at different times on account of varying climatic conditions and 

 other factors. 



1936 - Smith, G. L. Percentages and causes of mortality of boll weevil stages within 

 the squares. J. Econ. Ent. 29( 1 ):99- 1 05. 



During the cotton fruiting season, 1929-31, inclusive, fallen squares and 

 flared and damaged squares hanging on the plants were collected at about 15-day 

 intervals in June, July, and August from 8 fields in Louisiana representing dif- 

 ferent soil types. Examination of this material showed the percentage mortalities 

 of all stages of the boll weevil in hanging squares to be 4.3% in 1929, 12.06% in 

 1930, 9.24% in 1931, and 11.63% in 1932. The corresponding percentages for 

 fallen squares were 11.42%, 41.33%, 15.33%, and 24.08%. 



Temperature is the most important element in the climatic factor and has 

 the greatest effect on squares on the ground, exposed to the sun. The effective 

 fatal maximum temperatures lie from 93°F. upward, varying in efficiency almost 

 directly with increase above that figure. A single day much above 95°F. is suffi- 

 cient to produce heavy mortality in stages in contact with the earth and fairly 

 exposed to the action of the sun. With rainfall much less than l|- inches over the 

 15-day period, mortality was likely to be high, whereas precipitation in excess 

 of that amount tended to reduce mortality. This correlation is not thought, how- 

 ever, to be direct, but to be due to the effect of moisture upon temperature. 



138 



