Thermal-Summation Model
Definition
The linear model that relates insect development rate to temperature above a threshold. Development rate increases in proportion to the excess temperature; the inverse of the rate gives the time to complete a stage at a given constant temperature.
- Relationship
- Linear, rate versus temperature above threshold
- Core assumption
- Rate proportional to excess temperature
- Output
- Inverse of rate gives stage duration
- Use
- Basis for degree-day and degree-hour models
Common questions
What is the model's main limitation?+
It assumes a straight-line relationship across the full temperature range, but real development rates curve and slow near the lower and upper developmental thresholds, introducing error at temperature extremes.
How does the threshold temperature affect the calculation?+
Development below the threshold is assumed to be zero, so an inaccurate threshold value for the species used shifts every downstream degree-day or degree-hour estimate built on it.
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...
- Upper Developmental Threshold
- The temperature above which development decelerates. Between base and upper threshold the thermal-summation model is approximately linear; outside this range it breaks...