Zig-zag Elm Sawfly - Aproceros leucopoda

The easiest way to record this species is from the zig-zag feeding pattern made by the larvae in the leaves of Elm.  As the larva grows it eventually consumes the whole leaf, and whole plants can be defoliated. The adult is a small black, wasp-like sawfly with white legs. The larvae are tiny green caterpillars.

Adult Larval workings

Adult: Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

May occur wherever Elm is present.

Larval workings may be observed whenever Elm is in leaf.

Adult sawflies lay their eggs into the serrations at the edges of elm leaves and the larvae hatch within 4 to 8 days. The larvae develop over a further 15 to 18 days, spending this time feeding on the leaves. They then cocoon on the underside of the leaf, emerging as adults within 7 days. As the lifecycle is very short, the elm zig-zag sawfly can produce several generations in one summer and infestations can happen very quickly. Adding to this, no males of the species have been recorded which means the sawfly might reproduce by parthogenesis (reproduction without fertilisation) so its numbers can increase rapidly.

In Britain this sawfly is mainly recorded from the south-east of England and the East Midlands but spreading. It was introduced to Europe in 2003, spreading rapidly and reaching the UK by 2017.

Once rare in Leicestershire and Rutland, but now much more frequent in our area.  The record of 15th September 2020 is believed to be the first for VC55.

https://www.sawflies.org.uk/aproceros-leucopoda/