THE TOBACCO BEETLE. 



17 



over the top, about the same number being placed on each " hand." 

 The box, thickly wrapped with cloth and paper to avoid sudden 

 changes in temperature, was kept in a warm place where proper 

 breeding conditions could be maintained. At the end of three months 

 the tobacco was examined. The degree of infestation found is given 

 in Table I. 



Table L- 



-Preference shown by larrw of the tobacco beetle (Lasioderma ser- 

 ricorne) for different types of leaf tobacco. 



Type of leaf tobacco. 



Virginia heavy dark export, smoke-cured , 



Tennessee heavy dark export, smoke-cured . 



Burley, medium grade 



Ohio cigar leaf, medium-grade filler , 



Cuban cigar leaf, Santa Clara, medium light 



Florida shade-grown, light ci^ar wrapper 



Carolina bright yellow, flue-cured (thin and poorly cured) 



Egg 

 distributed. 



July 10,1914 



do ... 



do 



do 



do 



do 



do 



Tobacco 

 examined. 



Oct. 10,1914 



do 



do 



do 



do 



do 



do 



Degree of infes- 

 tation. 



Slight. 



Do. 

 Moderate. 



Do. 

 Heavy. 



Do. 



Do. 



Strong, heavy types of leaf tobacco ordinarily are not injured to 

 any great extent unless stored for a long time. Leaf tobacco which 

 is " fire " or smoke cured, such as that grown in the " dark-tobacco " 

 sections of Virginia or the " black-patch " sections of Kentucky and 

 Tennessee, is seldom seriously injured. This, perhaps, is due in 

 part to the flavor or quality given the leaf by the smoke, which acts 

 as a repellent, whereas the same type of leaf flue cured is readily 

 attacked, although not to so great an extent as are lighter-bodied 

 types of tobacco. These types, as well as all others, however, are 

 more apt. to suffer injury after the leaf has aged. The changes 

 brought about by long storage of any tobacco seem to make it more 

 suitable as food for the beetles. 



LENGTH OF LAKVA STAGE. 



At ordinary room temperatures in summer the larva or feeding 

 stage extends over a period of from 30 to 70 days ; the length of the 

 period depends mainly on temperature and on the character and 

 condition of the food substance. There is always considerable 

 variation in the length of the larval period, even with larvae from 

 the same egg lot, kept in the same food substance, and under the 

 same conditions. In cold weather the larva? become dormant and 

 may remain in this condition for several months. The insect passes 

 the winter mainly in this stage in cool climates. When the larvae 

 have finished feeding and are encased within the pupal cells, they are 

 able to stand considerable cold and are more resistant to the action 

 of fumigants. Activity in the larva stage ceases at temperatures 

 ranging from 60° to 67° F. At Clarksville, Tenn., larvae which 

 75257°— 19— Bull. 737 2 



