[a] The length of the spruce beetle life cycle is highly dependent on the rate of heat accumulation. In warm summers, spruce beetle can complete its life cycle in 1 year. The duration of the life cycle affects the assessment of risk and hazard of damage.

[b] Spruce beetle must overwinter as an adult before emerging to attack new host material. In the normal life cycle of two years, spruce beetle overwinters as a larva in the first year and as an adult in the second.