The eggs of five species of Delia have been examined for the external chorionic patterning, the size and shape of the micropyle and the number, characteristics and distribution of the aeropyles using the scanning electron microscope. The species concerned are the cabbage root fly Delia radicum, the onion fly Delia antiqua, the seed corn maggot Delia platura, the wheat bulb fly Delia coarclata and the turnip fly Delia floralis.

Each species has its own clear characters and this, coupled with a significant difference in egg size, enables one species to be distinguished from another.