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 I.—Preference shown by larve of the tobacco beetle (Lasioderma ser- 
ricorne) for different types of leaf tobacco. 
e 4 : ? Egg Tobacco Degree of infes- 
Type of leaf tobacco. distributed. | examined. tation. 
Virginia heavy dark export, smoke-cured...........------ | July 10,1914 | Oct. 10,1914 | Slight. 
Tennessee heavy dark export, smoke-cured -.....-.-...-.-|.,--- Gla aasosalonoe GOs aac Do. 
Burleyeame dium yet ad ener cet cee seme cen scence eee lea ecrs Goes Serer doses Moderate. 
Ohio cigar leaf, medium-grade filler...............--.--..- esse DOnde/-2ea|2esee Gojoe Do. 
Cuban cigar leaf, Santa Clara, medium light.---.......... | Beier 6 a ein, Sa etal GOs Heavy. 
Florida shade-grown, light cigar wrapper-.--.......------.|.---- dos aeee 59 ee doa cox Do. 
Carolina bright yellow, flue-cured (thin and poorly cured).|..... Cleese gee, GO eee 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 1s 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 LARVA 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 larve from 
the same egg lot, kept in the same food substance, and under the 
same conditions. In cold weather the larve 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 larvee 
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., larvee which 
75257°—19—Bull. 737-2 
