The last tergite of the abdomen has a strong, projecting spike, thus giving the group its common name of horntail. This is a very large (up to 4 cm long) sawfly with a distinctive yellow and black banded abdomen.

Indicator Species - Leicestershire, Leicester & Rutland Local Nature Recovery Strategy.

Photographs required.

Usually found in or near coniferous woods.

May to October.

Urocerus gigas targets weakened, dying, fire-damaged, or freshly felled coniferous trees. It cannot digest raw wood fiber (lignin and cellulose) on its own and relies on an obligate mutualism with a wood-rotting basidiomycete fungus, Amylostereum chailletii. By colonizing freshly dead timber, it initiates wood decay processes in conifer canopy gaps, opening up structural wood to saproxylic fungi, beetles, and microbial communities. The female wasps carry fungal spores inside specialized internal pouches at the base of their ovipositor. When laying eggs deep into conifer wood, the female injects both eggs and fungal spores. The fungus spreads through the xylem, breaking down dense lignin and softening the wood and the wasp larvae feed on the fungal hyphae and the pre-digested wood pulp created by the fungus.

Widespread.

Uncommon.

https://www.sawflies.org.uk/urocerus-gigas/