CONTROL OF INSECTS IN TOBACCO 7 



Mating and egg laying usually begin within 24 hours after emer- 

 gence. The average female probably lays more than 100 eggs, and 

 as many as 279 have been recorded. The eggs hatch in 3 to 17 days, 

 and the larvae reach maturity in 25 to 128 days. The pupal stage 

 requires from 5 to 25 days. Under summer conditions the life cycle 

 from egg to egg averages approximately 50 days— 5 days for incuba- 

 tion, 35 days for larval development, and 10 days for pupation. The 

 adult moths may live as long as 7 or 8 days — longer in cool weather. 

 The four stages of this insect are shown in figure 4. 



Figure 4. — Stages of the tobacco moth: A, Large larva; B, pupa; C, adult; D, eggs 

 and young larva on section of leaf tobacco. Approximately X 7. 



Seasonal Occurrence 



The tobacco moth passes the winter as a larva. In the fall most 

 of the mature larvae leave the tobacco and migrate to cracks and crev- 

 ices about the building, where they spin the loose cocoons of silk in 

 which they hibernate. Some larvae may spin cocoons on or near the 

 surface of the tobacco. Immature larvae may remain in the tobacco 

 in an inactive state, and probably many of them fail to survive the 

 winter. However, relatively few immature larvae enter the winter. 

 Once hibernation has begun, the larvae seem able to withstand low 

 temperatures for long periods. Larvae have been reported to sur- 

 vive the winter in unhealed buildings in Canada at a temperature of 

 — 30° F. In North Carolina and Virginia larvae have been known 

 to survive exposure to near-zero temperatures for periods of 2 to 3 

 weeks. 



At Richmond, Va., pupation usually begins in April, and emergence 

 of the first brood of moths generally starts in May. At Charleston, 

 S. O, and Wilmington, N. O, moths may emerge as early as the last 

 week of March. 



The peaks of emergence of the broods of the tobacco moth are a 

 little more sharply defined than those of the cigarette beetle. In the 



