Responses of Stomoxys Calcitrans (L.) to Radiant Energy and Their Relation to Absorption Charcteristics of the Eye

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Abstract
Spectrophotometric analysis showed the. cornea of both sexes to have absorption characteristics such as to affect only slightly the qualitative responses of the stable fly to radiant energy in the region 260 mμ to 750 mμ. Water solutions of the eye pigments, analyzed spectrophotometrically, showed increasingly strong absorption from the blue to the ultraviolet (more pronounced in the male than in the female) and an increased transmittance into the infrared. Behavioral studies showed that responses were independent of the absorption spectra of the corneas and inversely related to the transmittance qualities of the eye pigments, the response decreasing as pigment transmittance increased and vice versa. This lends support to the hypothesis that the eye pigments serve to isolate individual ommatidia and to increase the orienting ability of the insect to a light source. When flies were exposed to radiant energy of low intensity in the region 365 mμ to 730 mμ, both sexes responded maximally in the region 365 mμ to 465 mμ and again at 640 mμ. When high intensity was used, males showed four response peaks, at 390 mμ, 440 mμ, 515 mμ, and 640 mμ, respectively, whereas the responses of females gradually decreased from 365 mμ to 575 mμ and then peaked again at 640 mμ. An attempt to detect a photolabile shift in the eye pigments was unsuccessful. The reported absence of vitamin A in this fly, the response maxima of the insect, and the absorption characteristics of the eye pigments all lead to the suggestion that the stable fly may possess more than one photolabile pigment and does not have the rhodopsin system.

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