Spectral sensitivity of the compound eye of the cabbage root fly, Delia radicum (Diptera: Anthomyiidae)

The spectral sensitivity of the compound eye of the cabbage root fly, Delia radicum (Linnaeus), was measured using the electroretinogram (ERG) technique, at fifteen selected wavelengths between 340 nm and 670 nm. The form of the ERG was found to be diphasic in nature. A primary peak of spectral sensitivity in the UV (340-350nm), and a smaller secondary peak in the blue-green region (460-546 nm) were found, together with a shoulder of sensitivity, representing a 'pseudo-peak' as reported for other Diptera, in the red region (630 nm). No significant differences were found between the dorsal and ventral regions of the eye. The peak response in the green region (546 nm) agrees well with existing behavioural data on colour attraction and visual discrimination of host plants by the cabbage root fly.