10 farmers' bulletin 846. 



ment of larvae are a suitable food substance in a compact or con- 

 centrated form, high and uniform temperature, high humidity, and 

 protection from strong light and from rapid evaporation. 



The pupal cells. — After the larvse have become fully grown and 

 ready to transform to the pupa stage they construct cells or cocoons, 

 usuall}' within the food substance. In leaf tobacco these cells usu- 

 ally are found along the midrib or in folds of the leaf. In boxes 

 of cigars some of the cells may be found between the cigars and 

 the sides of the box, but the greater number are found within the 

 cigar. In leaf tobacco the cells frequently are incomplete, the larvae 

 using folds of the leaf for part of the cells. Within dense sub- 

 stances the surrounding material forms the necessary protection, 

 the walls of the cell being fragile and thinly lined. The cells are 

 more or less egg-shaped and about one-fifth of an inch long. Often 

 they are without definite shape. 



The prepupa stage. — Before transformation to pupae there is or- 

 dinarily a period of from 4 to 12 days during which the larvae 

 within the cells undergo structural changes, but if exposed to low 

 temperatures they may remain in the cells for a considerable time 

 before these changes take place. Before changing to pupae the 

 larvae lie in a curved position within their cells, and their move- 

 ments cause the cells to become considerabh^ larger than the larvae. 

 Their bodies then contract and become more deeply wrinkled. 



THE PUP^. 



The pupa stage of the tobacco beetle at room temperatures during 

 the warmer months of the year lasts from 5 to 10 days. The average 

 of 38 records obtained at Tampa, Fla., during July, 1913, was found 

 to be 7.8 daj's. 



THE ADULTS. 



When the change to the beetle or adult stage has taken place the 

 beetles remain inactive in the cells for from 3 to 7 days. After 

 emerging they remain at rest for a day or more, their color gradually 

 deepening to reddish brown. At first the beetles are comparatively 

 soft, and they do not attain their final degree of hardness until they 

 are ready to moA'e away from the pupal cell. They crawl or flj^ 

 about actively and are capable of flying for a considerable distance. 

 They avoid intense light and move about most actively in subdued 

 light or in darkness. When in the dark they are attracted toward 

 subdued daylight or to artificial light. In tobacco warehouses they 

 may often be found in large numbers at the windows in late after- 

 noon, the flight toward the windows being heaviest at sunset. Dur- 



