NUMBER OF GENERATIONS. 



The number of annual generation.s of the bollworni in the cotton 

 belt vaiies from about four to seven, dejK^ndino- on th(! latitude, with 

 an avcu'age of about five. Owing to the irregularity in time of appear- 

 ance of moth.s from the ground in the .spring and the variation in rate 

 of growth of different individuals f i-om various causes, there results a 

 considerable breaking up of geniirations, so that these arc rarely 

 marked. Thus, in 1903, in Texas, the insect in all stages, from cg^ to 

 adult, was to be found in considerable numbers in the same field at 

 any given time throughout the season. This condition, however, may 

 have been due in part to the lateness of the season. Furthermore, 

 there may be numerous distinct generations in the same locality, or 

 even on the same plantation, depending on the relative age of the 

 different fields of corn. It is therefore evident that in considering the 

 generations of the bollworm only the majority of the individuals may 

 be referred to. 



In general, the moths are out in maximum numbers in the spring 

 in any localit}^ in the cotton belt at a time when field corn is mostly 

 from 8 to 20 inches high, and they deposit by far the greater part of 

 their eggs on these plants. The first generation of boUworms feeds 

 mostly on the tender central roll of leaves of the j^oung corn, the moths 

 from these larvse appearing during late May or early June. These 

 likewise oviposit largely on corn, which by this time may be com- 

 mencing to ta,ssel somewhat and to show young ears, the larvte feeding 

 on the buds, unfolding tassels, and forming ears, as the case may be. 

 Moths from this, the second, generation of larvae make their appear- 

 ance from late .fune until early July and deposit eggs on corn, espe- 

 cially on the silks, which are now appearing quite generalh'. The 

 third generation of bollworms infests the soft milky ears of corn dur- 

 ing early July, and the moths appear again late in July or early 

 in August. By this time, however, the corn throughout the country 

 has begun to dr}'^ and the ears to harden and is no longer attractiv(; to 

 the moths for egg laying. They therefore fly to neiglil)oring cotton, 

 from which they secure nectar as food, and oji which they deposit the 

 greater part of their eggs. The more or less sinuiltaneous hardening 

 of corn during late Jul}^ results in a general migration of the moths 

 to the cotton fields, and injury to cotton during August from the 

 fourth generation of bollworms may often be very extensive. Not 

 infrequently, however, cotton may be severely ravaged by the fifth 

 generation during late September or early October. Larva? of the 

 fifth generation attain full growth usually by the middle of ()ct()l)er, 

 burrow into the ground, and transform to pupa», in which condition 

 the majority remain during the winter, the moths appearing the fol- 



191 



