68 BULLETIN 737, U. S. DEPARTMENT OF AGRICULTURE. 



extending from end to end, and placed so that the rays penetrate 

 the humidor from various angles. A rotary fan forces cold air 

 through the tube compartment and over the tubes, keeping the tem- 

 perature of the humidor normal. The finished cigars in closed 

 boxes are placed on a long shelf extending along the partition of 

 fibrous material (permeable to the rays) separating the tube com- 

 partment from the rest of the humidor. An exposure of 42 minutes 

 is given by an automatic control of current. Cigars are left on the 

 shelf until all space is taken up, then placed in other parts of the 

 humidor, where they are kept until shipped out. This arrange- 

 ment gives a minimum exposure, close to the Rontgen tubes, of 42 

 minutes. Ordinarily the method of handling gives many repeated 

 exposures, on the shelf close to the tubes or at distances farther out 

 in the humidor. A test of this process was made by the writer on 

 November 7, 1916, to determine the effect on the egg stage of the 

 tobacco beetle. About 200 eggs deposited on leaf tobacco were 

 placed in a sealed cigar box and treated. An equal number of 

 eggs were kept as a check. The eggs treated were placed in the 

 humidor 7| feet from the wall of the tube compartment and given 

 three periods of 42 minutes' exposure; then placed on the shelf di- 

 rectly in front of the tubes and given one period of 42 minutes' ex- 

 posure. This gave a total of three accumulative periods of 42 

 minutes each 7^ feet from the nearest tube and one period of 42 

 minutes on the shelf close to the tube compartment. By Novem- 

 ber 18 most of the check eggs had hatched, but all of the treated eggs 

 were more or less shrunken and none had hatched. 



SUMMARY AND RECOMMENDATIONS. 



The tobacco beetle, a stored-product insect, is practically cosmo- 

 politan and occurs wherever large quantities of leaf or manufactured 

 tobacco are handled or stored. It attacks a variety of dried sub- 

 stances, its most common food being tobacco. 



In tobacco factories, the principal sources of infestation of the 

 finished products are: 



(1) Infested leaf tobacco brought into the factory. 



(2) Tobacco warehouses, where beetles are present in large numbers, close 

 to the factory. 



(3) Infested tobacco, refuse material, cigars, or manufactured tobacco which 

 has accumulated. (Beetles breeding from this material quickly spread to all 

 parts of the factory.) 



A very few beetles present in storage or packing rooms in factories 

 may be the cause of serious loss, by depositing their eggs on the 

 finished product. The protection of the product at this time is 

 usually of more importance than the condition of the raw material, 

 since the leaf tobacco in most cases is partly or completely freed from 



