Iris Sawfly

There are more than 500 species of sawfly in the UK, which usually feed only on their preferred host plants. You will see iris sawfly (Rhadinoceraea micans) on waterside irises like the yellow flag irises at the QEII pond, though the larvae can eat rushes too.

The adults emerge in Spring after overwintering in the soil as pupae. They are black and hairy, about 8mm long, and have smoky grey wings (though they don’t fly much).

In April and May, a female will lay her eggs inside the base of an iris leaf near the thicker middle, cutting a slit with the tiny saw on her ovipositor. The larvae, which hatch in late May and June, grow to around 25mm.

The larvae are browny-grey with black heads and white spots along their bodies. Munching first on the edges of the leaves, in a group

 they can devour whole leaves, but the plants will recover next year.

Come July and they will crawl into the ground and make their cocoons to stay safe until next year.

Links to further information and images

Royal Horticultural Society

Naturespot