Effect of Variable Rates of Daily Sampling of Fly Larvae on Decomposition and Carrion Insect Community Assembly: Implications for Forensic Entomology Field Study Protocols

Abstract

Experimental protocols in forensic entomology successional field studies generally involve daily sampling of insects to document temporal changes in species composition on animal carcasses. One challenge with that method has been to adjust the sampling intensity to obtain the best representation of the community present without affecting the said community. To this date, little is known about how such investigator perturbations affect decomposition-related processes. Here, we investigated how different levels of daily sampling of fly eggs and fly larvae affected, over time, carcass decomposition rate and the carrion insect community. Results indicated that a daily sampling of <5% of the egg and larvae volumes present on a carcass, a sampling intensity believed to be consistent with current accepted practices in successional field studies, had little effect overall. Higher sampling intensities, however, slowed down carcass decomposition, affected the abundance of certain carrion insects, and caused an increase in the volume of eggs laid by dipterans. This study suggests that the carrion insect community not only has a limited resilience to recurrent perturbations but that a daily sampling intensity equal to or <5% of the egg and larvae volumes appears adequate to ensure that the system is representative of unsampled conditions. Hence we propose that this threshold be accepted as best practice in future forensic entomology successional field studies.

Environmental and evolutionary factors favouring the coexistence of sarcosaprophagous Calliphoridae species competing for animal necromass

“…To ensure that the first calliphorid of the calendar year was recovered and because rapid changes in the species assemblage early in the season were anticipated (see Michaud et al ., 2010), sampling began after snow melt on 10 May 2019 and new traps were set on a biweekly basis until June 28. Then, new traps were set on a weekly basis from 2 July to 12 August because calliphorid assemblages change little during the summer months (Michaud & Moreau, 2013, 2017). Thereafter, traps were set once every 2 weeks until 15 November because species richness declines during this period (Michaud et al ., 2010).…”

A preliminary investigation of the entomofauna composition of forensically important necrophagous insects in Al-Madinah Al-Munawwarah region, Kingdom of Saudi Arabia

“…The necrophagous species, particularly those of the dipteran families, are the most important in the estimation of the mPMI because of their association with a body immediately after death and because they are usually the most dominant species on a corpse [16]. Many factors may influence the insect succession and taxonomic diversity reported between present and previous studies such as, sampling frequency and number of animal models [27].…”

The Pitfalls in the Path of Probabilistic Inference in Forensic Entomology: A Review

“…Temporal effects occur because the same experimental units (i.e., carcasses/cadavers) are sampled over and over during most forensic studies. In addition to sometimes causing oversampling problems [33], this leads to an interrelation of the samples over time. Moreover, repeated samples cannot be considered random because a sample taken at time 1 is necessarily collected before a sample at time 2.…”

“…For examples of discriminant analysis, see studies on saproxylic beetles such as [50] or on dung beetles such as [51]. For examples of MANOVAs in a forensic context, see [33,40,52,53].…”