. Biology of the tobacco moth and its control in closed storage. Tobacco moth; Tobacco moth Control; Tobacco Storage Diseases and injuries. 20 CIRCULAR 4 2 2, U. S. DEPARTMENT OF AGRICULTURE In order to show graphically the seasonal occurrence of the tobacco moth in 1932 and 1933 the data are presented in figure 8. The spring brood of moths, which is composed of a small percentage of the first- generation larvae, approximately 50 percent of the second, and all of the third of the preceding year began pupating approximately March 15, and emergence began approximately April 10. These dates are b
. Biology of the tobacco moth and its control in closed storage. Tobacco moth; Tobacco moth Control; Tobacco Storage Diseases and injuries. 20 CIRCULAR 4 2 2, U. S. DEPARTMENT OF AGRICULTURE In order to show graphically the seasonal occurrence of the tobacco moth in 1932 and 1933 the data are presented in figure 8. The spring brood of moths, which is composed of a small percentage of the first- generation larvae, approximately 50 percent of the second, and all of the third of the preceding year began pupating approximately March 15, and emergence began approximately April 10. These dates are based upon laboratory life-history studies and many observations made in tobacco factories and warehouses during the period 1932 to 1934 in Virginia and North Carolina. CONTROL NATURAL ENEMIES The tobacco moth has an important enemy in the small braconid parasite Microbracon hebetor (Say) (fig. 11). The sting of this small wasplike insect in a well-grown larva of the moth results in complete paralysis of the larva in a few minutes. Eggs are then deposited be- neath or attached to the body of the host larva. These eggs hatch in about 2 days, when the tem- perature is above 70° F., and the young parasite grubs feed voraciously on the body of the moth larva. A total of 1,900 egg-to-adult rearings of the para- site were made in the laboratory, grown larvae of the tobac- co moth being used as hosts, and records of egg deposition and longevity were com- pleted for 14 females. A summary of these records shows the fol- lowing averages: Incubation period 2 days, larval period days, pupal period days, egg-to-adult period days. The highest number of eggs obtained from one female parasite was 517 and the lowest was 96. The average of the 14 females was 323 eggs each. The temperatures ranged from 65° to 85° during the time the fore- going records were being obtained. The shortest egg-to-adult period recorded for the tobacco moth was 39 days (table 6). It is estimated that und
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