NATIVE RANGE: East Asia

FIRST FINDING IN SLOVENIA: 2011

PATHWAYS: hitchiker with goods

POSSIBLE TO FIND: May-September

FLIGHT SEASON OF ADULTS: May-September

DESCRIPTION: A wasp with a black body and white legs, 6 mm long. The larvae are caterpillar-like, 10 mm long, with 2 to 3 pairs of thoracic legs and 8 pairs of prolegs on the abdomen. On the 2nd and 3rd pair of thoracic legs they have characteristic dark brown T-shaped marks. The larvae feed on elm leaves, causing characteristic zigzag-shaped damage and extensive infestations may defoliate entire trees. The species overwinters as a pupa in leaf litter.

HABITAT: On the leaves of elms (Ulmus spp.) in forests, rural areas and in urban green areas.

STATUS: Widespread throughout most of Europe, but in low numbers.

SIMILAR SPECIES: Several small, black sawfly species of the genera Pseudaprosthema, Pseudarge, Kokujewia and Aprosthema are very similar and cannot be distinguished with the naked eye, differing in wing-patterns, host plants and the pattern of damage they inflict on the host’s leaves.

SOURCE: Field Guide to Invasive Alien Species in European Forests