Hemichroa australis (Serville, 1823)

Hemichroa australis - Bicolorous Sawfly

North to northern Scotland, seemingly common and widespread (Musgrove, 2024).

In the female, the head and mesonotum and the underside of the antennae are orange-red whilst the underside of the thorax and the abdomen are entirely black. The costa is yellow with the stigma and remaining venation dark. In the male, the antennae are similarly red below and with a dark stigma.

Hemichroa australis larvae usually feed singly on the leaves of alder or birch. Initially they feed on the leaf creating a J-shaped hole in the leaf blade. Later instars feed at the edge of the leaf, eating the entire leaf. The tail is held curled downwards. Mature larvae have yellow heads with a black eye spot. The thoracic segments have yellowish spiracular and suprapedal lobes. The tail of the larva is marked with yellow dorsally.

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Size: Female: 5 - 8mm, male 5 - 6mm

GB IUCN status: Least Concern
GB rarity status: None

Distribution: England, Scotland, Wales, Ireland

Flight period: Bivoltine, May to June and July to August

Plant associations: Alnus spp. and Betula spp. (alders and birches)