12 CIRCULAR 4 2 2, U. S. DEPARTMENT OF AGRICULTURE 



LIFE-HISTORY STUDIES OF 1932 AND 1933 



Following previous studies (18) moths of the spring brood were 

 collected from tobacco warehouses in Richmond in 1931, and labora- 

 tory rearings were obtained from these and a continuous record kept 

 of the development of some of their progeny through the spring 

 of 1934. 



JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV D|C 



Figure 8. — Seasonal occurrences of the stages of the tobacco moth in Virginia and North 

 Carolina, based on laboratory life-history studies and on observations made in tobacco 

 warehouses, 1932 to 1934. 



METHODS AND APPARATUS 



To obtain egg-laying records pairs of moths were placed in indi- 

 vidual glass vials in which were portions of leaves of flue-cured 

 tobacco. The vials used (fig. 9) were 4% inches high and 1 inch in 

 diameter, and each was covered by a closely fitting metal cap. Every 

 24 hours the exposed pieces of tobacco were removed from the vials 

 and fresh pieces substituted, and all eggs laid during the interval 

 were counted with the aid of a binocular microscope. During incii- 



FlGURE 



Metal-capped glass vials used in ovipositiou studies on the tobacco moth. 



bation the groups of eggs, usually attached to the leaves (fig. 4), 

 were left in vials and examined daily for hatching. 



When the eggs hatched, the young larvae were transferred individu- 

 ally from the vials and placed on tobacco in pasteboard pill boxes 1% 

 inches in diameter and three-fourths of an inch deep. These pill 

 boxes were kept in large metal boxes that conserved the moisture, 

 holding the moisture at about 13 percent while the larvae were 

 developing. Portions of flue-cured tobacco leaves and parts of leaves 



