Philadelphia, Sept. 15, 1906.
To the Editor:
—The editorial reference in The Journal, September 15, page 865, to some observations on the preferences of mosquitoes in the matter of clothes, leads me to call attention to a source of error in such experiments. Some years ago a bulletin of the Hygienic Laboratory of the United States Public Health and Marine-Hospital Service detailed experiments on different colored stuffs with a view of determining if mosquitoes possess color preferences. I have not the bulletin at hand, but my recollection is that yellow was found to be least sought.The error that enters into such tests is that the avoidance of some colors may be due to the odor of the dyestuff and not to the color. Many of the yellow colors now in use are nitroderivatives, and even a very minute exhalation of a nitrocompound would be likely to be objectionable to