Contarinia oregonensis (Cecidomyiidae)
Douglas-fir cone midge
||This is not the injurious stage. Adult flies are small,
only 3-4 mm long. Adults have just 1 pair of wings. Abdomen is orange, and
female flies have a long retractile ovipositor.
||Mature larva is small and orange coloured. The feeding larvae
live in small chambers within the seed. The unusual chamber formation
as a plant response to feeding by larvae results in galls being formed.
||Adult female lays eggs near base of cone scale in newly
opened flowers. When the egg hatches, the larva tunnels into the young cone
scale and forms a gall. The gall fuses the developing ovule to the scale.
Severe infestations will destroy all seeds in the cone. The larva remains
in the cone until it completes its development, it drops to the ground during
wet weather in autumn. Cocoons are spun in the litter and overwintering occurs
in prepupal and pupal stages.
This insect probably occurs throughout the range of Douglas-fir, but it is
generally more serious in wetter coastal areas than in the drier interior.
References and Links:
EAG: 548; FC: 417.