Survival and development of the forensically important blow fly, Calliphora varifrons (Diptera: Calliphoridae) at consta
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ORIGINAL ARTICLE
Survival and development of the forensically important blow fly, Calliphora varifrons (Diptera: Calliphoridae) at constant temperatures Sasha C. Voss • David F. Cook • Wei-Feng Hung Ian R. Dadour
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Accepted: 5 April 2014 Ó Springer Science+Business Media New York 2014
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 ± 0.17 days at 27 °C to 49.93 ± 0.26 days 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 ± 26.38 K. 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. S. C. Voss (&) D. F. Cook W.-F. Hung I. R. Dadour Centre for Forensic Science M420, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia e-mail: [email protected]
Keywords Forensic entomology Temperature Development Calliphora varifrons Post-mortem interval Blowfly
Introduction The native Western Australian brown blowfly, Calliphora varifrons Malloch 1932 (Diptera: Calliphoridae), is an ovoviviparous species of forensic importance occurring in several high profile homicides in Western Australia. Primarily active in the winter–spring period, this species occurs in the southwest of Western Australia [1, 2]. Females arrive at remains within minutes of death and deposit live larvae [3]. Larvipositing blowflies have a competitive advantage over their oviparious, egg laying counterparts as their offspring can immediately commence feeding as opposed to first completing (*24 h) a stationary egg phase [3]. As one of the first species to arrive and colonize decomposing remains, C. varifrons is a useful indicator species of minimum time since
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