In forensic entomology, 'accumulated degree days' (ADD) is defined as:

• A The total number of calendar days since death multiplied by 24 hours
• B The mean ambient temperature divided by the number of larval instars observed
• C The sum of rainfall days that accelerate microbial decomposition
• D The sum of daily mean temperatures above the developmental threshold for the species, from the time of death to specimen collection ✓

Explanation

ADD is a thermal-time concept: insects develop at rates determined by temperature above their biological zero (developmental threshold, typically 10°C for many blow flies). ADD = Σ (daily mean temperature − developmental threshold) for each day from first oviposition to collection. A specific ADD value corresponds to a specific developmental stage for a given species. This corrects for temperature variations at different death scenes, making ADD far more reliable than calendar days alone.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.