Gall midges have been reported from cones of western red cedar, Thuja plicata Donn., but none have been described. Keen (1958) reported the occurrence in Washington and Oregon of a cone midge which was credited with destroying 90 per cent of the seed. In 1940 Prebble and Graham reported a midge in cones of western red cedar at Cowichan Lake, B.C. These reports almost certainly refer to the midge described here. The only other species taken from red cedar cones was Lestodiplosis taxiconis Foote, but it occurred in verysmall numbers; previously it has been reported only from cones of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco (Foote, 1956).