title: The distribution of blow fly (Diptera: Calliphoridae) larval lengths and its implications for estimating post mortem intervals.
abstract: The length or stage of development of blow fly (Diptera: Calliphoridae) larvae may be used to estimate a minimum postmortem interval, often by targeting the largest individuals of a species in the belief that they will be the oldest. However, natural variation in rate of development, and therefore length, implies that the size of the largest larva, as well as the number of larvae longer than any stated length, will be greater for larger cohorts. Length data from the blow flies Protophormia terraenovae and Lucilia sericata were collected from one field-based and two laboratory-based experiments. The field cohorts contained considerably more individuals than have been used for reference data collection in the literature. Cohorts were shown to have an approximately normal distribution. Summary statistics were derived from the collected data allowing the quantification of errors in development time which arise when different sized cohorts are compared through their largest larvae. These errors may be considerable and can lead to overestimation of postmortem intervals when making comparisons with reference data collected from smaller cohorts. This source of error has hitherto been overlooked in forensic entomology.
authors.affiliation: Department of Natural Science and Public Health, Zayed University, Dubai, PO Box 19282, United Arab Emirates. colin.moffatt@zu.ac.ae.|School of Forensic and Applied Sciences, University of Central Lancashire, Preston, PR1 2HE, UK. colin.moffatt@zu.ac.ae.
authors.forename: Colin
authors.identifier: http://orcid.org/0000-0001-5586-8980
authors.initials: C
authors.lastname: Moffatt
authors.affiliation: School of Forensic and Applied Sciences, University of Central Lancashire, Preston, PR1 2HE, UK.
authors.forename: Viv
authors.initials: V
authors.lastname: Heaton
authors.affiliation: School of Forensic and Applied Sciences, University of Central Lancashire, Preston, PR1 2HE, UK.
authors.forename: Dorine
authors.initials: D
authors.lastname: De Haan
mesh_terms: D000818:Animals; D004175:Diptera / Q000254:growth & development*; D004772:Entomology; D005247:Feeding Behavior; D018732:Forensic Anthropology; D049429:Forensic Pathology; D007814:Larva / Q000254:growth & development*; D015233:Models, Statistical; D011180:Postmortem Changes; D013552:Swine
keywords: Blow flies; Error; Forensic entomology; Postmortem interval; Statistical distributions