Rearing and sampling methods for estimating spruce budworm development rates at constant temperatures

We describe an experimental protocol for measuring the response of spruce budworm post-diapause larval development to temperature. This protocol is specifically designed to include measurements of development near their upper and lower thermal thresholds. The application of this protocol to a laboratory colony allowed for the first experimental evidence that spruce budworm larval development occurs at temperatures as low as 5 ºC and as high as 35 ºC and provides data to estimate development rates at temperatures from 5–35 ºC in 5 ºC increments. Our protocol is also designed to minimize mortality near the thermal development thresholds thus allowing for multi-generational studies. We observed developmental plasticity in larvae reared at constant temperatures, particularly the occurrence of up to 42% of some individuals requiring only five instars to complete development, compared to the expected six instars. An occurrence that exhibited no clear relation to temperature. While this protoc...