Intrinsic development rate of spruce budworm (Lepidoptera: Tortricidae) across a gradient of latitude

Development of the spruce budworm, Choristoneura fumiferana (Clemens), in the field varies with latitude but no satisfactory explanation for this variation has been provided. Theory suggests that the optimum temperature for development, the maximum development rate, and the range of temperatures over which development occurs, are adapted to local temperature regimes. To test this hypothesis, spruce budworm populations from locations spanning a 15 degrees range in latitude were reared on artificial diet, at 10 different constant temperatures ranging From 9.3 to 33 degrees C. However, these experiments yielded no evidence for adaptation in parameters controlling development rate. It is suggested that migration by egg laying moths undermines processes that might select for individuals adapted to local temperature regimes. Rapid development seen in northern populations of the spruce budworm is not apparently explained by thermal adaptations but might, instead, result from effects of photoperiod on feeding behavior.