190 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



ilized without any knowledge of the fact. This matter has been 

 investigated carefully by a number of students in France and Germany. 

 In fact, the histology of the organs subjected to the rays has been 

 determined with great care. It has been found that certain bodies 

 of cells are remarkably susceptible to the rays and that their func- 

 tionality is entirely destroyed although morphologically they seem 

 to be almost normal. 



During the past year by accident the writer and several of his 

 associates have had an opportunity to conduct a number of experi- 

 ments with Roentgen rays. In these experiments special attention 

 has been directed toward the determination of the question of whether 

 the sexual organs of insects are affected in any manner analogous 

 to that in the case of human beings, guinea pigs, rabbits and other 

 animals with which the experiments noted were performed. At 

 Dallas, Texas in April, 1911 the experiments were begun with Calandra 

 oryzae, several species of ticks, and two Isopods, Armadillidium 

 vulgare and Porcellio laevis. The manipulation in the experiments 

 with the rice weevil are typical of the procedure that was followed 

 in all cases. Grain containing large numbers of adults and immature 

 stages was exposed to the rays at different distances and different 

 periods. The exposure averages from ten to twenty seconds, the 

 distance from the tube from fourteen to twenty inches and the current 

 from five to seven milliamperes. After exposures according to this 

 plan large numbers of the adult beetles were taken from the cages 

 and placed in jars with grain which had been thoroughly sterilized 

 by means of heat. It was considered that observations as to whether 

 reproduction took place in this sterilized medium would show whether 

 any effect had been produced upon the reproductive organs of the 

 insect. 



In brief the experiments are negative. In all but two of the ten 

 experiments reproduction took place. It varied, of course, greatly 

 in the different jars but this variation did not seem to be correlated 

 with any differences in the treatment. In fact, the two series in 

 which no reproduction was found to take place represented the longest 

 exposure and the shortest. 



The next experiments were performed with ticks of various species. 

 The first series was designed to determine the effect of the rays upon 

 eggs of Margaropus annulatus which were on the point of hatching. 

 Such eggs were exposed from 1 to 15 seconds at a distance of from 11 

 to 18 inches, with a current of 5 to 7 milliamperes. In the exposed 

 lots from 10 to 70 per cent of the eggs hatched, in one of the controls 

 30 per cent, and in the other 50. It was not evident, therefore, that 

 the rays had any effect whatever upon the eggs. Another experiment 



