Examination of the effect of hydrated lime and bleach on the decomposition of remains and development of calliphora stygia

The larvae of necrophagous fly species are used in entomology for the estimation of post-mortem interval (PMI). However, substances applied to a corpse in a bid to accelerate the rate of decay or destroy evidence may affect the attractiveness and succession of a corpse to insects, and the subsequent decomposition of remains. Additionally, chemical substances may affect larval development and survival, leading to an inaccurate estimation of the PMI. The effect of these substances on larval growth, development and survival was investigated under laboratory conditions on the forensically relevant Australian blowfly species, Calliphora stygia, as well as the effects these substances have on decomposition of remains. It was found that the presence of these substances induced a significant delay in the pre-appearance interval (PAI) and oviposition during colder months in the Geelong region. Furthermore, remains which had been applied with the substances during Autumn and Spring did not skeletonise. Over Winter, the remains decomposed over a longer duration of accumulated degree hours (ADH), due to a lack of insect activity, with no remains skeletonising. Bleach and hydrated lime was shown to have no significant impact on the growth of C. stygia, however, hydrated lime significantly impacted the survival of C. stygia. Additionally, a significant difference in larval growth was observed between different feeding substrates; minced meat compared to non-minced meat. The presence of these substances was able to be detected in C. stygia using High-Performance Liquid Chromatography (HPLC) through all developmental stages; it is suggested that further chemical analysis such as Mass Spectroscopy be used in conjunction with HPLC analysis for chemical composition and quantification. These findings show the importance of considering the presence of bleach and hydrated lime on remains when estimating PMI, and the unreliability of utilising minced liver to replicate remains in entomological research.