. Circular. Insect pests; Insect pests. METHODS OF CONTROLLING TOBACCO INSECTS. Table I.—Average length of different stages in life history of the southern tobacco hornvorin (Pilegethontius sexto). Emer- gence of moth to ovi- posi- tion. Incu- bation period. Instars, or stages, in growth of larva. Total p , Total larval ,,., ; lifp period. Perw'1- cycle. First. Second. Third. Fourth. Fifth. Days. 4 Days. \ Day*. 4 3 Days. 3 Days. Days. 3 4- Days. 6. 5 Days. Dni/s. Days. 21 48. Fig. 9. The Southern tobacco hornworm: Larva, fourth instar. Natural size. (Original.) The tobacco moths, as has
. Circular. Insect pests; Insect pests. METHODS OF CONTROLLING TOBACCO INSECTS. Table I.—Average length of different stages in life history of the southern tobacco hornvorin (Pilegethontius sexto). Emer- gence of moth to ovi- posi- tion. Incu- bation period. Instars, or stages, in growth of larva. Total p , Total larval ,,., ; lifp period. Perw'1- cycle. First. Second. Third. Fourth. Fifth. Days. 4 Days. \ Day*. 4 3 Days. 3 Days. Days. 3 4- Days. 6. 5 Days. Dni/s. Days. 21 48. Fig. 9. The Southern tobacco hornworm: Larva, fourth instar. Natural size. (Original.) The tobacco moths, as has already been stated, begin to emerge from hibernation about June 1, or slightly earlier, and the emgrgenct continues until the middle of August or later. From Table I we see that 48 days after the emergence of the moths from hibernation the moths of the second generation will become adult, and that in 4 days more they will begin to deposit eggs. These egos will hatch in 4 days, and in 6 or 7 days more—that is, in about two months from the emergence of the first moths from hibernation —the larva1 of the second generation will pass into the third instar, the instar in which they begin to injure tobacco seriously. For example, let us take 4 moths that have emerged from hi- bernation on the following dates: June 1, June 15, July 1, and July 15. The second generation of to- bacco worms, the progeny of these moths, will begin to injure tobacco seriously about August 1, August 15, September 1, and September 15, respectively. Although moths of both the first and second generations are depositing eggs during late July and in August, we will show later that by far the greater percentage of them has just emerged from hibernation, and belongs, therefore, to the first generation. This fact has a very important bearing upon the recommendation of fall plowing. Tobacco worms begin to enter the soil to pass the winter (i. e., hibernate) about the middle of August, and continue doing so un
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