Mayetiola thujae, the redcedar cone midge, is a species of gall midge that infects western redcedar (Thuja plicata) cones.
Males are 2.44mm long on average. Females are somewhat larger, averaging 2.77mm in length, and have retractible ovipositors.[1] The adults of both sexes are dark gray.[2]
Eggs are laid on the inner surface of female western redcedar cones in the March or April,[3] shortly after pollination occurs.[4] The eggs are oblong and translucent, but appear to be orange due to the color of the larvae.[4] The eggs hatch in April or May after a month of incubation.[3] The larvae, which grow up to 4mm long,[2] feed on the seeds and tissue of the cone before beginning to pupate in late summer.[4]
As a control measure, insecticides can be applied to western redcedar cones in the spring.[2] The larvae are often infected by parasitoid wasps of the family Chalcididae.[4]