It is unique for each insect, species but also measurable for each insect species. This usually results in a positive linear relationship between temperature and insect development rate. The inverse of the slope of the linear relationship reflected in a regression equation technically equals the number of degree days it takes for the median of a population to reach the next lifestage. Describe how you would calculate degree-day accumulation in the field. For each day, the mean temp above the low threshold equals the number of degree days accumulated for that day.
Adults emerge from soil in the spring.
They go to the leaders of young trees 3 - 15 years, mate and then the females oviposit in the bark of theleaders. The result brood of grubs begin feeding on phloem under the bark and feed together as the move down the leader. They will eventually bore into the stem to pupate and emerge as adults in the late summer. The adults overwinter in the soil. This causes forking and bushiness in the tree.