What role do developmental temperature thresholds play in PMI estimation?

• A. They measure maximum temperatures during development
• B. They are not used in PMI estimation
• C. They define the minimum temperature for development for each species; used to adjust growth models to local conditions and estimate PMI
• D. They indicate when eggs hatch regardless of temperature

Answer: (C)

The role of developmental temperature thresholds is to set the minimum temperature at which an insect species can progress through its life stages, and to use that boundary to translate observed insect development into a time since colonization. In forensic entomology, each species has a lower developmental threshold below which development effectively stops. When estimating PMI, we look at the ambient temperatures since death and accumulate degree-days above that threshold. By matching the accumulated degree-days to the species’ known development timeline, we back-calculate how long the insects have been developing, giving an estimate of when colonization occurred. This approach requires adjusting growth models to local environmental conditions, since temperature histories vary by location and season. The threshold is not about maximum temperatures, nor is development independent of temperature; it directly informs how quickly development can proceed under the local climate, which is essential for accurate PMI estimation.