REARING DIAPAUSE AND DIAPAUSE-FREE WESTERN SPRUCE BUDWORM (CHORISTONEURA OCCIDENTALIS) (LEPIDOPTERA: TORTRICIDAE) ON AN ARTIFICIAL DIET

Abstract

The western spruce budworm, Choiistoneura occidentalis Freeman, which normally passes through an obligate diapause in nature, was reared in the laboratory without diapause. The critical factor for preventing diapause appeared to be the physical environment presented to the first stage larvae. The response of C. occidentalis was flexible. The 2nd stage larvae could be made to diapause or forego diapause, depending on their rearing experience in the first stage. By eliminating diapause it was possible to rear about 7½ generations per year as against about 2¼ under normal diapause conditions. The diapause of the jack-pine budworm, C. pinus pinus Freeman, and C. lambertiana californica Powell, could be prevented by the same technique. The diapause of the spruce budworm, C. fumiferana (Clemens), could not be eliminated except after several generations of selection.