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 (ER G) technique, at fifteen selected wavelengths between 340 nm and 670 n m. The form of the ERG was found to be diphasic in nature. A primary p eak of spectral sensitivity in the UV (340-350nm), and a smaller secon dary peak in the blue-green region (460-546 nm) were found, together w ith a shoulder of sensitivity, representing a 'pseudo-peak' as reporte d for other Diptera, in the red region (630 nm). No significant differ ences were found between the dorsal and ventral regions of the eye. Th e peak response in the green region (546 nm) agrees well with existing behavioural data on colour attraction and visual discrimination of ho st plants by the cabbage root fly.