April, '12] HUNTER: COTTON MOTH OUTBREAK 127 



frequent references are made to a theory that was propounded in 

 1846 to the effect that outbreaks are to be anticipated at intervals of 

 21 years. This theory was proposed after the great outbreaks of 

 1783, 1804, 1825 and 1846, which, as will be noted, mark regular 21 

 year periods. In 1846 it was confidently predicted in the press in the 

 south that the next outbreak of the moth would occur in 1867. That 

 year displayed no alarming outbreak of the moth, somewhat to the 

 discomforture of the believers in the theory of 21 year cycle. The 

 following year, however, 1868, witnessed one of the most extensive 

 defoliations that has been placed on record. Reallj', therefore, it 

 may be considered that the outbreak of 1868 is in the regular 21 year 

 sequence. Twenty-two years from 1868 marks the last of the out- 

 breaks prior to 1911 of which we have any record. It is very striking 

 to note that the outbreak of 1911 is exactly 21 years after that of 1890. 

 Among the eight great outbreaks of Alabama argillacea which have 

 been recorded, extending from 1783 to 1911, there is only one which 

 does not fit into the 21 year cycle theory. This is the one which 

 occurred in 1872-3. The writer confesses that he is inclined to dis- 

 credit the theory and is considerably surprised to find that there 

 seems to be but one marked exception. Probably the matter may 

 be explained as a series of coincidences but this is not cjuite satisfactory 

 on account of the great regularity in the series. 



The most interesting feature of the invasion of 1911 from the ento- 

 mological standpoint is the effect that it had upon the boll weevil. 

 In one way the caterpillar acted very decidedly against the weevil 

 but in another way it favored it. The injurious effect was the result 

 of defoliation of the plants. This allowed the light and heat of the 

 sun to reach the infested squares on the ground and naturally cause 

 the death of many of the weevils in their immature stages. Moreover, 

 the defoliation caused the complete cessation of the growth of the 

 plant so that no fruit was available for the weevils that succeeded in 

 emerging from sheltered conditions on the ground. On the whole 

 the effect of the defoliation was extremely disastrous to the weevil. 

 In fact, this important check coming as it did at the end of a series of 

 three consecutive seasons in which the climatic conditions were very 

 unfavorable for the weevil was a very important factor in the produc- 

 tion of the remarkably large cotton crop of 1911. 



The other effect which the cotton caterpillar had upon the 

 weevil was to increase the extent of the dispersion movement in 

 the late summer and fall. The defoliation was generally practi- 

 cally complete at the normal time of the height of the dispersion 

 movement. The weevils would arise from a field and fly to another 

 which they would find defoliated and then set out upon a series of 



