Mayetiola thujae

Mayetiola thujae, the redcedar cone midge, is a species of gall midge that infects western redcedar (Thuja plicata) cones.

Description
Males are 2.44 mm long on average. Females are somewhat larger, averaging 2.77 mm in length, and have retractible ovipositors. The adults of both sexes are dark gray.

Ecology
Eggs are laid on the inner surface of female western redcedar cones in the March or April, shortly after pollination occurs. The eggs are oblong and translucent, but appear to be orange due to the color of the larvae. The eggs hatch in April or May after a month of incubation. The larvae, which grow up to 4 mm long, feed on the seeds and tissue of the cone before beginning to pupate in late summer.

As a control measure, insecticides can be applied to western redcedar cones in the spring. The larvae are often infected by parasitoid wasps of the family Chalcididae.