86 THE MEXICAN COTTON -BOLL WEEVIL. 



the two status examinations made in 1910 in southern Mississippi 

 it was very evident that in these fields in which cotton followed corn 

 there was a conspicuous ahsence of infestation until the fall dis- 

 persion of 1910, whereas in neighboring fields in winch cotton fol- 

 lowed cotton the infestation was in some cases extremely high, even 

 in June. 



These circumstances and many others which have been observed 

 in the spring indicate a rather irregular dispersal from the places of 

 hibernation which may carry the weevils considerable distances in 

 all directions. On the extreme border of the infested territory this 

 may result in the infestation of entirely new territory. 



SPRING SPREAD WITHIN THE FIELD. 



The spread from plant to plant begins in the portions of the field 

 adjacent to favorable hibernation quarters. It has usually been 

 found that the early summer infestation begins at a point adjacent 

 to timber or near farm buildings where seed or seed cotton has been 

 stored. From these centers it is generally easy to trace the infesta- 

 tion to other parts of the field. The movement of the weevils from 

 these centers, however, is not regular. They occasionally fly to 

 rather distant portions of the field and then start new centers, but 

 on the whole the progress is steady and soon brings about a complete 

 infestation of the field. 



A number of observations were made to determine the degree of 

 movement of hibernated weevils in a field at Victoria, Tex., in 1904. 

 The weevils were marked so that they could be recognized, and 

 frequent examinations were made to determine the location of each 

 specimen from day to day. 1 It was found that the maximum time 

 one weevil remained upon a single plant was 18 or more days, the 

 observations having been discontinued after the eighteenth day. 

 The average time positively found in 73 cases was 4 days, with a 

 possibility for this same number of observations of 6f days. Prob- 

 ably a true average lies approximately between these results, and, 

 if so, we may assume that about 5^ days usually intervene between 

 the movements of each weevil. In the whole series of observations, 

 extending over 25 days, for weevils which were found after being 

 liberated, only 57 movements were recorded. The total of these 

 movements averaged only 62 feet each in 177 movement days. This 

 would give us an average movement of but 0.35 foot per day for each 

 weevil in a field where stubble plants were quite abundant, where 

 squares were forming upon fully one-third of the plants, and during 

 a period for which the mean average temperature was 78.6° F. 



SUMMER FLIGHTS. 



During the summer there is more or less general movement within 

 the cotton fields and also from field to field. These flights are at 

 first weak, but gradually become more pronounced and finally lead 

 into the great dispersal of the late summer and fall. 



During the summer the conditions on the border of the infested 

 area are peculiar. Many of the weevils which arrived late in the fall 

 of the preceding ye&v are unable to survive the winter on account of 



i Phe remainder of this paragraph is from Bulletin 51, Bureau of Kntomology, p. 112. 



