Survival and development of the forensically important blow fly, Calliphora varifrons (Diptera: Calliphoridae) at constant temperatures.

Abstract

The influence of temperature on the development of the forensically important blow fly, Calliphora varifrons Malloch 1932 (Diptera: Calliphoridae), was investigated at seven constant temperatures ranging from 12 to 30°C. C. varifrons completed development between 12 and 27°C. At 30°C larvae formed pupae but did not successfully emerge. Temperature significantly influenced development time, mortality, maximum larval length, and adult body size. Development time (larviposition to adult emergence) ranged from 16.65±0.17days at 27°C to 49.93±0.26days at 12°C. Development rate was essentially linear throughout the 12-27°C temperature range. Linear estimates of lower developmental threshold and thermal requirement (K) for development of C. varifrons were 4.20°C and 368.46±26.38K. At 30°C, a slight inhibitory effect of high temperature on third instar development rate was observed followed by a rapid decline when subsequent development and survival ceased. Nonlinear estimates of lower developmental threshold for third instar development were comparatively higher (6.29°C). Nonlinear estimates of optimal developmental temperature and upper lethal developmental threshold were 25.94 and 32.13°C respectively. Mortality was high at both temperature extremes (12 and 27°C) and lowest between 18 and 24°C. Maximum larval length was inversely related to temperature. Adult body size was significantly smaller at 12°C, peaked at 18°C, and declined as temperatures increased. The species-specific development data presented are the first available for C. varifrons for use by forensic practitioners for estimation of minimum time since death.