Calliphora vicina (Diptera: Calliphoridae) larvae are developmentally impaired in the presence of decomposed liver

There are numerous biotic factors that affect the development rates of blow fly (Diptera: Calliphoridae) larvae, and an understanding of these effects is necessary in order to make accurate minimum postmortem interval (PMImin) estimates. Previous research uncovered differences in development rates of larvae reared on different tissues and on differentially processed tissues. This difference suggests that more emphasis should be made on the selection and state of larval diets for the purposes of creating accurate developmental data. Newly hatched Calliphora vicina Robineau-Desvoidy larvae were reared at 23°C on either decomposed (for 7 days); fresh whole; frozen/thawed; or minced swine liver. Five larvae, one from each of five cups, were randomly sampled every 6 h for the first 84 h, after which, five larvae were sampled once daily until pupariation. Length and instar were recorded as well as time to reach developmental events, pupariation and eclosion. Development rate was significantly (P < 0.001) slower, by as much as 30 h (55.4% of total development time) for mid-sized larvae, and 71 h (35.0%) and 58 h (14.6%) if using times to the onset of pupariation and eclosion, respectively, than immatures that developed on fresh whole swine liver. Development rates of larvae reared on decomposed liver were also slower than larvae reared on minced swine liver and frozen/thawed swine liver. Time to reach developmental events were significantly affected (P < 0.001) in the decomposed treatment, however duration of pupariation was unaffected. In conclusion, these results suggest that any estimate of a PMImin may result in an over estimate if the blow flies used were developing on an already decomposed body.