The size of fly larvae is an important variable in the use of these insects to estimate postmortem interval. Furthermore, the nutritional intake of larvae is likely to vary subject to the part of a corpse on which they are feeding. A study was therefore conducted to investigate the effect of type of food substrate on larval growth in two species of forensically important Australian blowflies. After collection on sheep's liver in the laboratory, different groups of larvae of Lucilia cuprina (Wiedemann) and Calliphora augur (Fabricius) were grown on sheep's liver, meat, and brains, and their body lengths compared. Results indicated that the development of larvae fed sheep's liver was adversely affected compared with larvae fed meat and brain; they moulted later, reached maximum length more slowly and sometimes produced significantly smaller pupae. These findings, similar to those of another recent study, have obvious implications for postmortem interval determinations. Estimates may be considerably skewed if the site of collection of larvae at a death scene contains tissue types different to those used in reference experiments. We therefore recommend caution in forensic analyses that interpret crime scene data using developmental studies performed with a single type of larval food substrate.
While research has examined the effect of freezing and subsequent thawing on the decomposition of carcasses, no studies have investigated the effect of the freezing and thawing of tissues used as a developmental substrate by fly larvae. This paper reports on the results of such a study using larvae of Calliphora augur (Fabricius) on sheep's liver. Approximately 20 first-instar larvae were collected on sheep liver and subsequently transferred to paired treatments of fresh and frozen/thawed liver equilibrated to room temperature. They were then left undisturbed for 1-10 days. When the allocated time had elapsed, the body length of the larvae in each pair of groups was compared. No significant differences were detected between any pairs at a 1% level and only one pair was significantly different at a 5% level. We conclude that freezing and thawing of a developmental medium of sheep's liver has no significant effect on growth of C. augur larvae.
Calliphora augur (Diptera: Calliphoridae) is a common carrion-breeding blowfly of forensic, medical and agricultural importance in eastern Australia. Despite this, detailed information on the developmental biology of C. augur is lacking. Here, we present the first comprehensive study on the development of all three larval instars of C. augur, fed on sheep's liver, at constant temperatures of 15, 20, 25, 30 and 35°C. We provide thermal summation models describing instar duration, as well as 95% prediction intervals for larval length at each constant temperature, enabling the age of larvae of C. augur to be estimated from their developmental stage and their average length. These data provide a basis for the application of this species to forensic investigations.
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