Spatial dispersion of post-feeding larvae of forensically important flies: Implications for medicolegal investigation

Abstract

Introduction

Calliphoridae flies allow estimating the postmortem interval (PMI), as they are the first to arrive at a decomposing body. Its larvae feed on the carcass and then move away to pupate (post-feeding dispersal). Since the environment alters the physiology and behaviour of insects, the dispersal of larvae and the final location of pupae could be related to the place where the carcass is deposited. The aim of this work was to study the dispersal of post-feeding larvae in relation to environmental variables in northern Patagonia.

Materials and methods

The distribution of pupae in response to different illumination, temperature, and soil inclination conditions was evaluated. A circular box divided into quadrants was used for each treatment and a control. Post-feeding larvae were placed in the centre of each box, allowing them to disperse until they pupate. Differences in the number of pupae collected in each quadrant were evaluated by × ² tests.

Results

According to the control, the dispersion of post-feeding larvae occurs randomly (p = .098). Regarding temperature, the larvae eluded the heat source (p < .01). The inclination treatments showed that larvae avoided the raised surface (p < .01). Concerning illumination conditions, no trend was observed (p = .41).

Conclusions

Knowing the dispersal patterns of larvae, considering environmental variables, reduces search times and let infers the sectors with the highest probability of finding pupae. In this way, it is likely to estimate a more precise PMI in the framework of medico-legal investigations.