Visual Sensitivity of Four Strains of Screwworm Flies

Visual sensitivity of flies of 4 colonized strains of screwworms was compared by use of an electroretinogram (ERG) technique. Flies of newly colonized strains were more visually sensitive than those from strains that had been colonized for long periods of time. Flies of the newly colonized strains were more like native flies both in visual sensitivity and in distribution of visual responses than were flies of the older strains. In overall mean response, females of each strain were visually more sensitive than males of the respective strains. Visual sensitivity of males and females peaked between 3 and 5 days of age. Visual sensitivity of males usually peaked earlier than that of females and decreased significantly as age increased.