Western larch sawfly

Latin name: Anoplonyx occidens Ross
French name:
Order: Hymenoptera
Family: Tenthredinidae

Description

Distribution

British Columbia

This species occurs throughout the host range in British Columbia; it also occurs south to Washington and Montana.

Micro-habitat(s)

Needle

Damage, symptoms and biology

The western larch sawfly is a common, frequently abundant and rarely destructive defoliator. Damaging outbreaks have not been recorded in British Columbia but have been in Idaho and Montana.

Mature larva up to 21 mm long. Head, brown with black eyes. Dark grey dorsum except for a light grey middorsal stripe; light grey below the spiracular line. Seven pairs of abdominal prolegs.

This species overwinters as a prepupal larva in a cocoon buried in the soil. Adults emerge from late May to June and the females lay eggs, usually singly, in needles. Larvae are present from mid-June to July. Mature larvae drop to the ground and spin cocoons from late July to August.