Western redcedar cone midge
Mayetiola thujae
Life history: One generation per year. Adult emerges in early spring (March) during redcedar pollination period. After mating, female midges lay eggs on pollen-receptive seed cones.
Egg: orange-red (vermilion) and cylindrical, about 0.8 mm long by 0.2 mm wide. Contrast with green colour of cones makes redcedar cone midge eggs relatively visible to the naked eye.
Eggs are found on or between cone scales either singly or in groups numbering up to 45.
Larva: Eggs hatch in April and developing larvae feed throughout the cone, each destroying more than one seed. Larvae are orange, about 3-4 mm long when fully grown, and generally resemble the shape of the eggs. Larvae may be found anywhere within the cone tissue.
Pupa: In late summer / early fall, each larva constructs a thin, white, papery puparium within which it turns into a reddish brown pupa and rests through the winter. Pupation is completed in the late winter. Pupae that are ready to emerge as adults become much darker and some adult features can be seen under their "skin".Life history
Adult: The small, (about 3 mm long), dark grey, mosquito-like adults have clear wings with a small number of distinct veins. There are many species of midges that look like this and field identification of redcedar cone midges is difficult to do unless the adults are reared from redcedar seed cones, captured in traps baited with cone midge sex pheromone, or observed laying eggs on cone scales.
Damage: Redcedar cone midge larvae feed on scales and seeds throughout individual cones. Each larva is capable of destroying more than one seed.