Canadian Forest Service Publications
The reactions of the housefly, Musca domestica Linn., to light of different wave-lengths. 1938. Cameron, J.W.M. Canadian Journal of Research 16:307-342.
Issued by: Great Lakes Forestry Centre
Catalog ID: 35214
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Houseflies were reared on an artificial medium and tested with different wavelengths of spectral light obtained from a quartz-mercury arc. The spectrum tested extended from X3022 A to X57S0 A, and the lines were made of approximately equal intensity throughout. In addition, X5-1-61 A and X-I-078 Awere tested at several other intensities. The comparison standard in all cases was 'white' light, obtained from a tungsten-filament, inside-frosted bulb, and filtered through copper sulphate solution. It was of constant quality, and the intensity was varied by changing the size of the bulb and by varying the distance from the bulb to the copper sulphate filter. The lighted areas to which the flies reacted were 5 by 10 mm. On one of these fell a total intensity of colored light of approximately 10.3 microwatts, on the other a range of intensity of white light of from 0.34 to 36. I J.LW. Flies to be tested were removed from the breeding cage ten hours before tests began and were kept in darkness until used. Each fly whose record was used in compiling the final results was caused to make ten trips towards the two test lights, and a record was kept of the choice on each trip. A description and discussion of the four different methods found in the literature for conducting experiments of this type. and for analyzing the results, arc included. In the first method, the intensity of the test light of a given wavelength is kept Constant, while that of the standard light, usually white, is varied until both are equally attractive. The second method involves testing the colored light against a fixed intensity of white and finding the ratio of insects attracted to color. The intensity of white that will give the same ratio of attractiveness when tested against the standard is then determined. In the third method, the two test lights are made equal in intensity, and their relative efficiency is considered to be directly proportional to the number of insects attracted to each. In the last method, the standard is kept"fixed in both quality and intensity, and the intensity of the test color is varied until the two arc equal in attractiveness. Application of the first three methods to the same data shows that they give results that vary greatly as the intensity changes. Some show that efficiency increases as the intensity increases, while others show a decrease in efficiency with increasing intensity. If the intensities of all colored lights are equal, the three methods give practically the same qualitative results when applied to the s.,l,me data. That is, a curve of efficiency is found which has its peak at the same wave-length, whatever method is used. Quantitatively, the results given by the three methods differ, so that no definite ratio of attractiveness can be determined between colors. The data obtained were not amenable to analysis by the fourth method, but published results indicate that this is perhaps the best method for determining the quantitative relation between the stimulative efficiencies of light of different colors.