THE TOBACCO BEETLE. 9 



80° F. nearly all hatch the sixth or seventh day after they are laid. 

 Cool weather may retard hatching- for a considerable time. 



THE LARV^. 



Xewly hatched larvae are somewhat more active than later, and 

 owing- to their extremely small size readily enter boxes or containers 

 holding tobacco. AVhen exposed to light, the larvse disappear within 

 the food substance or under cover as quickly as possible. They are 

 able to ci-awl for short distances and often migrate from infested to 

 uninfested material. This habit sometimes accounts for the quick 

 appearance of injury in freshly made cigars. Partly grown larvae 

 shaken from leaf tobacco have been found on cigar makers' tables. 

 These larvae easily enter the open ends of the cigars, and in a very 

 short time their work may be noticed in the bundle or box of fin- 

 ished cigars. Several cigars in a box or package may be injured 

 by a single larva. Preference is shown for the thinner or chaffy 

 leaves of cured tobacco, and for certain tj^Des of high grade that 

 are mild and sweet flavored. (See fig. 3.) Strong, heavy types of 

 leaf tobacco ordinarily are not injured to such an extent as are the 

 milder or thinner types, unless stored for a long time. Leaf tobacco 

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

 tobacco sections of Virginia and in the " black patch " of Kentucky 

 and Tennessee, seldom is badly injured. This is due in part, perhaps, 

 to the flavor or quality given the leaf by the smoke, as well as to the 

 natural qualities of tobacco of this type. The smoke seems to act 

 for a time as a repellent, since the same type of leaf, flue cured, is 

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

 types. These types, as well as all others, however, are more likely 

 to be injured after the leaf has become aged. The changes brought 

 about by long storage of any tobacco seem in some way to make it 

 more acceptable as food for. the larvae. 



Length of larva stage. — At ordinary room temperatures in summer 

 the larva or feeding stage extends over a period of from 30 to TO 

 days, depending mainly on the temperature and on the character, 

 abundance, and condition of the food. In cold weather the larvae 

 become dormant and may remain in this condition for some time. 

 It is mainly in this stage, in cool climates, that the insect passes 

 the winter. When the larvae have finished feeding and are in- 

 cased within the pupal cells they are able, either as larvaei or 

 as pupae, to stand a considerable degree of cold. Larvae within 

 the cells are also more able to resist treatment with fumigants. 

 Activity in the larva stage ceases at temperatures ranging from 

 60° to 67° F. The most favorable conditions for rapid develop- 



102001°— Bull. S46— 17 2 



