Necrophagous diptera are used in forensic entomology to measure the post-mortem interval (PMI) of cadavers. PMI estimates based on fly larvae, however, can be inaccurate when larval development is retarded, or accelerated, by the nutritional composition of the cadaveric tissue. We compared the post-embryonic development of Chrysomya putoria (Wiedemann, 1830) on different tissues of pigs and cows. Forty newly hatched fly larvae per treatment were placed on 60 g of the following swine tissues: liver (T1), swine lung (T2), swine heart (T3), swine muscle (T4), bovine heart (T5), bovine lung (T6) and bovine muscle (T7). There were four replicates/treatment. Experiments were conducted in controlled conditions (28°C day/26°C night, RH 70% ± 10% and 12 h of photophase). Fly larvae reared on swine liver took longer to develop (5.2 days) than flies reared on other substrates (from 3.5 to 4.5 days), and this difference was statistically significant. The total duration of development on swine liver (T1) was significantly slower (8.7 days) when compared to the other treatments. Larvae reared on swine lungs (T2) were significantly heavier in the third instar (x = 61.2 mg) than larvae reared on swine liver (T1), swine muscle (T4), bovine lung (T6) and bovine muscle (T7). Total larval survival was high (above 76%) in all treatments except for T1 (66%). There was no deviation from the expected adult sex ratio, and the percentage of abnormalities remained within the expected range. These results reinforce the idea that, to achieve greater accuracy in PMI estimates, the type of tissue on which the larvae develops needs to be taken into account.
In forensic entomology, the minimum and maximum post-mortem interval (PMI) is estimated on the basis of the developmental stages of necrophagous Diptera larvae on a corpse. The nutritional composition of the decomposing tissue, which can influence larval development rates, may impact the precision of this estimate. We compared the post-embryonic development of Chrysomya albiceps reared on bovine muscle and swine lung. Forty newly hatched fly larvae, per treatment, were placed on 60 g of the following tissues: bovine muscle (control) and swine lung (T1). Each treatment had three replicates. The experiments were maintained under controlled conditions (28°C day/26°C night, 70 ± 10% RH and 12 h photophase). Flies reared on bovine muscle took significantly longer to complete their larval phase (8.1 days) than did larvae reared on swine lung (6.8 days). The total duration of development in bovine muscle was significantly slower (12.3 days) than in swine lung. Larvae that were reared on swine lungs were significantly heavier than larvae reared on bovine muscle. Total larval viability was high on pig lung (over 49%). The sex ratio was closer to the 1:1 ratio in bovine muscle (rs = 0.55), with a slightly greater proportion of female larvae. The percentage of abnormality remained within the predicted range. The results show that the different tissues influenced larval development. This underlines the importance of considering the type of cadaveric tissue when larval development is used to calculate the minimum PMI in forensic investigations.
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