Wavelength-discrimination behavior in the grasshopper Phlaeoba.

The grasshopper Phlaeoba sp. has ocular filters that are arranged in discrete retinal bands. These filters modify the spectra of some of its photoreceptors, all of which are apparently filled with the same resident photopigment. The receptor response differences produced by the ocular filters provide a potential basis for wavelength discrimination. Behavioral tests of wavelength discrimination in Phlaeoba were therefore run; they confirmed earlier qualitative findings that indicated that Phlaeoba can discriminate between visual stimuli on the basis of wavelength cues and quantitatively showed that the behavioral preference is proportional to the receptor spectral difference. Tests of animals with indistinct retinal bands indicated that wavelength discrimination was reduced in this variant but was still quantitatively related to the receptor spectra. These data suggest that the filter-mediated color vision hypothesis applies in the case of Phlaeoba.