The Spinach Stem Fly Hylemyia echinata (Séguy), is an important pest of spinach (Spinacia oleracea) grown in the east and south-east of England for canning and freezing. Attack by the larvae results in the blackening and distortion of terminal shoots and the splitting and discoloration of petioles and mid-ribs, and some larvae may be present in the crops when they are harvested.

The eggs are laid in May on the upper surfaces of the leaves and among the leaflets of the terminal and axillary buds. The larvae penetrate the epidermis and tunnel through the mesophyll until they reach mid-ribs, petioles or stems where they feed on the hollow inner surfaces. The puparia are usually found in the soil but may occur in the feeding sites. The second generation emerges in June and July, and further emergences occur in August and September. Larvae are present in the crops from May to October.

Eggs and larvae are described and illustrated so that they can be distinguished from those of the Mangold Fly, Pegomyia betae (Curt.), which are often present on spinach at the same time. The flies are described and the characters which distinguish them from the Bean Seed Flies, Delia cilicrura (Rond.), are noted.