Thermal summation model and instar determination of all developmental stages of necrophagous beetle, Sciodrepoides watsoni (Spence) (Coleoptera: Leiodidae: Cholevinae).

Pavel Jakubec

doi:10.7717/peerj.1944

Abstract

Necrophagous beetles are underrepresented in forensic entomology studies despite their undeniable utility for the field. In the present article, information is presented regarding the developmental biology and instar determination of Sciodrepoides watsoni (Spence, 1813), a very common species occurring across the Holarctic region. Wild collected beetles were kept in climate chambers at constant temperature (12, 15, 18, 21 and 28 °C) and their development was regularly documented. Parameters of thermal summation models and standard errors were calculated for each developmental stage. These models may be used for an estimation of post-mortem interval in legal investigations after further validation on local populations of S. watsoni. An additional methodology is introduced for future studies of size-based characteristics, addressing instar identification bias. The methodology provided estimations (mean, standard error and standard deviation) of S. watsoni larval head capsule width for preliminary larval instar determination. The methodology may be used with other morphological features to improve instar determination accuracy.

Highlights

Forensic entomology is a rapidly developing new field of science (Midgley et al, 2010)
PrePrints was overlooked for a long time (Midgley et al, 2010), there are only a three species of beetles with known thermal summation models (Midgley & Villet, 2009a; Velásquez & Viloria, 2009; Ridgeway et al, 2014)
A laboratory colony was started with adults of S. watsoni, which were collected in spring of 2012 and/or 2013 from five localities in the Czech Republic

Summary

Introduction

Forensic entomology is a rapidly developing new field of science (Midgley et al, 2010). A good example is the commonly used thermal summation model (Richards & Villet, 2008) This model, which is based on the assumption that development of immature stages is linear, has been known for several decades (Higley et al, 1986), but it is still not established for the majority of forensically important species of invertebrates, which would be a great contribution to legal investigations. They do not form a maggot ball like flies and they can be reared individually so they are easier to handle in laboratory conditions (Midgley et al, 2010)

Methods

Results

Conclusion