Strobilomyia neanthracina (Anthomyiidae)

spiral spruce cone borer

Formerly Hylemya anthracina, and Lasiomma anthracina

Adults:

Adult Strobilomyia neanthracina. This small black fly (approx. 6 mm long) looks a little like a housefly. It emerges from the cocoon in spring and searches for the female cones (megastrobili) on which it lays her eggs.



Larvae:

Mature Strobilomyia neanthracina maggot. The mature maggot is approx. 6 mm long with a pair of distinct black mouth hooks. Maggot drops to the ground and pupates in the litter in mid summer.



Damage:

Saggital section through cone demonstrating Strobilomyia larval tunnels and damage. Eggs are laid on cone scales in early May or June. Larvae feed for about one month, consuming seeds and scales around the rachis. From midsummer onwards, larvae tunnel to the surface of the cone and drop to the ground where they pupate. A single larva can destroy more than half of the seeds in one cone.



Principal Hosts:

White, Englemann, Sitka and black spruce.

Economic Importance:

This species is a major pest of spruce cones.

References and Links:

EAG: 548; FC: 428.

Additional Images:

Life cycle of Strobilomyia neanthracina. Life Cycle Diagram
Egg on cone scale in spring. Neat circular exit hole chewed by mature maggot. Puparia extracted from litter under infested trees.