THE TOBACCO BEETLE. 



49 



Table VII. — Effect of exposure of stages of the tobacco beetle (Lasioderma ser- 

 ricorne) to ultra-violet rays. Experiments at Clarksville, Tenn., 1916. 





Stage of 

 insect. 



Age of 

 eggs. 



Cur- 

 rent. 



Volt- 

 age. 



Exposure. 



Results. 



Date. 



Dis- 

 tance 

 from 

 mer- 

 cury 

 vapor 



arc. 



Time. 



Eggs on upper 



side of leaf; 



exposure 



direct. 



Eggs on under- 

 side of leaf. 



Eggs under 

 glass cover. 



1916. 

 July 20 

 Aug. 11 



Do... 



July 20 

 July 21 



Eggs 



do 



do 



do 



do 



do 



All stages.. 



Adults and 

 eggs. 



Days. 



1 



1-2 



4-5 



3 

 2 



4 

 1-3 



2-3 



Amp. 

 3.3 

 3.3 

 3.3 



3 



3.3 

 3 

 3.3 



3 



66-437 

 66-67 

 66-67 



70-75 

 66-67 

 70-75 

 66-67 



70-75 



Inches. 

 8 

 7.5 



S 



, ".5 



8 

 8 

 7.5 



8 



Min. 

 i 

 i 



5 



10 

 45 



8 



5 



None hatched 

 do 



Nearly all 

 hatched. 



None hatched 

 do 



All hatched . . . 

 do........ 



Hatching nor- 

 mal. 



do 



do 



All hatched. 



Do. 



Ha t c h i n g 



normal. 



Do. 



Do. 



July 24 

 July 20 



July 24 



Exposed directly to rays. Eggs sterilized. 

 No effect apparent on other stages. 



Exposed directly to the rays. Eggs steril- 

 ized. No apparent effect on adults. Fer- 

 tile eggs deposited after exposure . 



TRAPPING. 



ATTRACTION TO LEAF TOBACCO. 



In cigar factories it has often been noticed that the adult beetles 

 collect on hands of leaf tobacco suspended for the purpose of ascer- 

 taining the humidity. Eggs in large numbers frequently can be 

 found on the leaves, and in the rooms where cigars are made or 

 handled young larvae from these eggs may easily find their way to 

 the cigars. Numerous experiments were made by liberating large 

 numbers of the beetles in a closed room in which hands of leaf to- 

 bacco had been suspended about the walls. It was found that a large 

 proportion of the beetles collected on the tobacco. This habit of the 

 insect suggests the possibility, where conditions permit, of trapping 

 the adults in this manner. The tobacco could be collected at frequent 

 intervals and the eggs and beetles killed by heating or fumigating 

 the leaves, and then replaced ; thus, instead of being a source of in- 

 festation, this tobacco would to a large extent protect the cigars or 

 other material in the room. The method is said to have been tested 

 in a cigar factory in the Philippines and to have shown excellent 

 results (78). 



TRAP LIGHTS. 



The movement of adults toward light has been discussed under 

 ; ' Phototropism " (p. 25) . Specially constructed trap lights may often 

 be used to advantage in factories or warehouses, and a large number of 

 the beetles destroyed. A very efficient trap can be made quickly and 

 easily by pinning together sheets of sticky fly paper in the form of 

 a cylinder and suspending it around an electric light. The trap is 

 75257°— 19— Bull. 737 4 



