226 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



SOME EXPERIMENTS WITH ROENTGEN RAYS UPON THE 

 CIGARETTE BEETLE, LASIODERMA SERRICORNE FABR. 



By A. C. Morgan and G. A. Runner, Bureau of Entomology, U. S. Department 



of Agriculture 



In the Journal of Economic Entomology, Vol. 5, No. 2, pp. 

 189-192, Mr. W. D. Hunter brought the subject of the effect of the 

 Roentgen rays upon insects up to date, and discussed a large number 

 of experiments that were performed under his immediate direction. 

 He concluded that there was no indication that X-rays had any ef- 

 fect upon insects. 



In the fall of 1912, in pursuance with instructions from Mr. Hunter, 

 the writers proceeded to Tampa, Fla., to test an X-ray machine 

 built for "sterilizing" cigars upon a commercial scale. The promo- 

 ters claimed that this treatment would either kill or render harmless, 

 all stages of the cigarette beetle, that is, eggs would fail to hatch, 

 larvsB and pupae would cease to develop, and adults would lay sterile 

 eggs. Since it was possible to give somewhat longer exposures with 

 the Tampa machine than it was found possible to secure with the 

 apparatus at Mr. Hunter's command, and since the cigarette beetle 

 was not included among the species treated by Mr. Hunter, it is 

 thought that a brief discussion of the Tampa experiments might be 

 of interest to this Association. 



Briefly, the machine and the method of treatment may be described 

 as follows : The machine consisted of an alternating current transformer 

 with a mechanical rectifier; the rectifier is so adjusted that only the 

 peaks of the rectified waves are taken off the commutator and put 

 through the X-ray tubes. Therefore, the rays produced were of 

 high penetration but of comparatively low burning power, that is, 

 there was a minimum of the Gamma, or burning ray. Two 7-ineh 

 X-ray tubes of the self-regulating type are mounted in the leaded 

 exposure chamber. This chamber is six feet long, about two and a 

 half feet broad and two feet high; each tube is placed near opposite 

 corners of the box, about twenty inches from the ends and about 

 eleven inches above the belt carrier. During a commercial run the 

 carrier would move a box of cigars through the field of the rays in 

 nine minutes. The capacity of the machine is about 40,000 cigars a 

 day. 



The tubes are customarily started "hard" {i. e., with great resist- 

 ance), so they will back up a spark gap of 4 to 4|^ inches which is 

 equivalent to a voltage of from 64,000 to 70,000. The commercial 

 current passed through the tubes ranged from 1^ to 2| milliamperes, 



