2G5 



<ind the feeling of emulation among^ scientific workers quite commend- 

 able, yet in all of this activity it is well before one does the honors of 

 iutroducinji- to his fellows a new-found depredator to look well to it that 

 some one has not performed the same office even before the time of either 

 himself or his' immediate ancestors. The earlier agricultural and horti- 

 cultural publications of the country are fiill of references to the depreda- 

 tions of insects whose names, if they had any, were unknown to the 

 observer, yet often the most important characteristics are so clearly 

 described as to leave little or no doubt as to the species involved. 



THE COIOE OF A HOST AND ITS RELATION TO PARASITISM. 



By C. W. Stiles, Ph. D., and A. Hassall, M. K. C. V. S., Bureau of Animal Industry, 

 U. S. Department of Agriculture. 



In Prof. Wallace's book on Darwinism, it is stated that white cattle 

 are more subject to the attack of flies than dark colored cattle, and 

 that white fowls are more subject to the gape-worm disease than dark 

 fowls. In regard to the former statement, two explanations immedi- 

 ately occurred to us, i. e., (1) the flies would be more easily seen upon 

 a white background than upon a dark background, and the assumed 

 correlation between the host and its parasites would be in this case 

 only apparent, or (2) the white color might attract the flies more than 

 a dark color. It is, in fact, a common household belief that if ob- 

 jects of various colors are suspended from the ceiling of a room, the 

 light-colored objects attract the flies more than the dark colored ob- 

 jects. We can hardly see, though, how the white color of fowls can 

 stand in any relation to their Nematode parasites, since the latter have 

 no organs of sight, and the only explanation which we could imagine 

 was that the white fowls are constitutionally weaker than dark fowls, 

 and would on this account succumb more easily to the ravages of the 

 worms than darker fowls with hardier constitutions. There is, how- 

 ever, serious objection to assuming that white fowls are inferior to 

 dark fowls, since white breeds of fowls exist which are very hardy — the 

 White Leghorn, for instance. 



Upon inquiring among our friends we find the most contradictory 

 opinions in regard to the two statements by Wallace mentioned above. 

 Mr. Howard states that there is certainly no connection between the color 

 of cattle and the Horn-fly {Hccmatohia serrata); several persons have 

 noticed that white horses are attacked more by flies than dark horses, 

 while other persons are not willing to admit this statement. From two 

 sources we have the statement that on two farms it was very noticeable 

 that the white chickens were considerably weaker than the dark fowls, 

 while from other sources we have the opposite statement. 



In hopes of obtaining some decisive evidence for or against Professor 



