Upper Developmental Threshold
Definition
The temperature above which development decelerates. Between base and upper threshold the thermal-summation model is approximately linear; outside this range it breaks down and requires nonlinear corrections.
- Field
- Forensic entomology, thermal biology
- Effect above threshold
- Development rate decelerates
- Model validity
- Thermal-summation model linear only between base and upper threshold
- Outside range
- Requires nonlinear correction
Common questions
Why does development slow down above the upper threshold instead of stopping?+
Enzyme activity governing larval growth peaks at an optimal temperature and declines as heat stress increases past it, so metabolic processes continue but become less efficient rather than shutting off abruptly.
How does ignoring the upper threshold affect a PMI estimate?+
Applying a linear degree-day model to a heatwave period overstates accumulated development, which can bias the postmortem interval estimate toward a shorter time since death than actually occurred.
Related terms
- Accumulated Degree Days (ADD)
- The sum of daily mean temperatures above a threshold (usually 0 °C) over a period of interest. Used as a measure of...
- Accumulated Degree Hours (ADH)
- A temperature-corrected measure of developmental time. Calculated by summing (hourly ambient temperature minus the species-specific base temperature threshold) across the period of...
- Base (Lower Developmental) Threshold
- The temperature below which an insect species does not develop. For forensically important blow flies in temperate regions this typically ranges from...
- Scene Correction Factor
- A temperature offset derived by comparing data-logger readings at the scene with concurrent weather-station readings, then applied retrospectively to station historical data...
- Thermal-Summation Model
- The linear model that relates insect development rate to temperature above a threshold. Development rate increases in proportion to the excess temperature;...