388 Journal of Agricultural Research voi. vi, no. h 



tive results, hatching being apparently normal in treated eggs of both 

 species. 



The eggs of both the tent caterpillar and the tussock moth were nearing 

 the end of the incubation period when treated. In eggs of the tent 

 caterpillar embryonic development is practically completed in the fall, 

 the larvae remaining in the eggshells over the winter and emerging on 

 the appearance of warm weather in the spring. 



SUMMARY 



Under laboratory conditions tests made with a Rontgen-ray tube per- 

 mitting a high-energy input and giving an intense and powerful radiation 

 gave results which promise that the X-ray process may be successfully 

 used in treatment of cigars or tobacco infested with the tobacco, or ciga- 

 rette, beetle. 



Heavy dosages must be given, as is indicated by the exposure given in 

 the series of experiments tabulated in this paper. 



In treatment of the Q.gg stage, heavier exposures are required to sterilize 

 eggs which are near the hatching point than are required to sterilize eggs 

 newly laid. 



In experiments performed by the writer a dosage equivalent to 150 

 milHampere minutes exposure with a spark gap of 5.5 inches gave satis- 

 factory results with eggs in tobacco placed 7.5 inches from the focal spot 

 of the tube. With this exposure the eggs in which embryonic develop- 

 ment was well advanced hatched, but in all cases where these larvae were 

 kept under observation they failed to reach the adult stage. 



The minimum lethal dosage at a given distance from the focal spot of 

 the Rontgen tube used has not been determined. 



In two separate experiments adults were given an exposure of 600 

 milliampere minutes (amperage X time), with a spark gap of 5.5 inches, 

 giving an approximate voltage of 65,000, with humidity at ^j. The 

 distance from the focal spot of the Rontgen tube was 7.5 inches. The 

 results are as follows : 



(i) No effect on length of life was apparent, as the beetles died at about 

 the same rate as the same number of beetles kept as a check. 



(2) Large numbers of eggs were deposited after exposure. These eggs 

 were infertile. Eggs laid by the check beetles hatched normally. 



Larvae were given an exposure of 600 milliampere minutes, other con- 

 ditions of the experiment being the same as in the experiments with 

 adults given above. While no immediate effect was apparent, the treat- 

 ment had the effect of stopping activity and development, the larvae 

 remaining in a dormant condition for a prolonged period. All treated 

 larvae died before reaching the pupal stage. 



