The color of the counting area on the celluloid card should vary 
with the color of the insect. For example, for the spotted alfalfa aphid, 
which is pale greenish yellow, a dark background should be used. For 
the brown wheat mite and other dark species a white background is 
the most satisfactory. 
Literature Cited 
(1) hawson, F. R..D. Bb? Fox; and W. © Cook 
1941. Three new devices for measuring insect populations. 
U.S. Bur. Ent. and Plant Quar. E-183, 6 pp. 
