206 



THE CANADIAN ENTOMOLOGIST. 



CL 



i 



This is a curious case, showing an incom- 

 plete copying of the male characters, accom- 

 panied by considerable distortion. None of 

 the organs affected are perfect images of their 

 counterparts in the male, though the left 

 mandible is sufficiently near to suggest that 

 sex at once. 



The figures will show the mandibles from 

 above, the left on account of the downward 

 ^ curve of the tij), appearing shorter in propor- 

 tion than it should, and, owing to their position, 

 the lower series of teeth is not shown. 



COLOUR-BLINDNESS AMONG ENTOMOLOGISTS. 



BY PROF. C. H. FERNALD, AMHERST, MASS. 



It is well known that a small percentage of the people in this 

 country, and perhaps in all countries, are more or less colour-blind, and 

 it is a noteworthy fact that such persons are often entirely unconscious of 

 it or do not fully appreciate its disadvantages. The officials of the 

 railroads and certain other corporations test the applicants for situations, 

 and if they are found to be colour-blind, or not able to distinguish 

 colours accurately, they are not employed. It will be readily seen that if 

 a railroad engineer or the officer of the deck on one of our large 

 passenger ships could not distinguish between red and green signal lights 

 in the night, most disastrous accidents might be the result. 



An entomologist might be more or less colour-blind on some colours 

 and be entirely unconscious of the fact, but the results in his descriptive 

 work would be faulty and more or less misleading, according to the 

 degree of imperfection in his colour vision. A correspondent wrote me 

 a short time ago that he had a larva which he called green, but his 

 assistant declared it to be white. It is possible that if these gentlemen 

 were tested, the colour vision of one or the other would be found more or 

 less imperfect. 



It is to prevent any i^ossible errors in descriptive entomology 

 because of colour-blindness that we have adopted the plan of testing all 

 the graduate students in entomology in the Massachusetts Agricultural 

 College. 



