The leafminer adult is a small fly 2.5 – 3mm in length. The females puncture leaves with their ovipositor to lay eggs into the plant tissue. About 60 eggs can be laid over 3 weeks, which then hatch into larvae that burrow under the leaf surfaces. These ‘mines’ are a pale colour and become wider as the larvae develop. Larvae emerge from their mines to pupate on the leaf surface, or within the ground, when ready.