The Spectral Sensitivity of Calliphora Maggots

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Abstract
1. The relative spectral sensitivity of larvae of Calliphora vomitoria and C. erythrocephala has been determined, using the maggot's natural tendency to travel towards the weaker of two opposing lights. 2. The response to light at each wavelength between 402 and 602 mµ was the same for the two species, within ±0.1 log unit, and the results are well fitted by the bell-shaped curve characteristic of a (hypothetical) visual purple, maximal at 504 mµ. 3. Reduction of the intensity of the white standard light by one log unit did not change the shape of the curve, and the extended wavelength range, between 362 and 640 mµ, shows no sign of a subsidiary maximum of sensitivity. The levels of illumination were 10-2 and 10-3 f.c., and the absolute threshold was found to be about 10-6 f.c. 4. The spectral sensitivity found here is compared with the results of other workers for muscid flies and larvae. It is concluded that one of the independent maxima of sensitivity found in the flies is a continuance from the larval state.