Chronology of the Intrapuparial Development of the Blowfly Chrysomya albiceps (Diptera: Calliphoridae): Application in Forensic Entomology

Abstract

Insects display different patterns of development, and blow flies have one of the most specialized patterns of intrapuparial development of all. In forensic entomology, pupae can be used as a tool to estimate the minimum postmortem time interval (minPMI). We analyzed the intrapuparial development of Chrysomya albiceps (Diptera: Caloricidade), whose larvae had been fed pig lungs and reared in a climate-controlled room at 28°C day/26°C night, 70 ± 10% RH, and 12 h of photophase and monitored daily. After the third-instar larvae abandoned their diet, the process of pupariation and pupation was monitored. At pre-established times, five pupae were collected, euthanized, and fixed in 5% formaldehyde, inside polypropylene test tubes with caps. Since they were the first, they were classified as 0 h pupae. Twelve collections occurred until the emergence of the adults, at 0, 2, 4, 6, 8, 10, 24, 30, 48, 54, 72, 78, 96, and 99 h (n = 84). The fixed pupae were dissected under the microscope, with the aid of anatomical tweezers and hypodermic needles, and photographed. The stages of metamorphosis and the morphological alterations occurring during the process were identified, described, and recorded before and after pupation. These phases were: pupation, larval pupal apolysis, cryptocephalic, phanerocephalic, pharate adult, emergence, and adult. The cryptophalic phase occurred between 4 and 6 h after pupation; the phanerocephalic phase between 6 and 10 h after; the pharate adult phase between 24 and 96 h after; and the imago/emergence phase 99 h after pupation.

Eye-background contrast as a quantitative marker for pupal age in a forensically important carrion beetle Necrodes littoralis L. (Silphidae)

“…The significant advantage of the technique is its likely universality. The majority of intra-puparial development studies of flies included the eye color of a pupa 22 , 36 – 38 , 44 , 45 , 59 . When we investigated published pupal eye pictures 28 , 29 , 38 we found strong support for the prediction that our technique will work effectively with forensically useful flies, as well.…”

“…Most methods developed to age forensically relevant pupae are based on morphological analyses 7,22,25,[27][28][29]32,[34][35][36][37][38][39][40][41][42][43][44][45] . Such analyses require only a stereomicroscope and are generally non-destructive.…”

“…yellow, reddish etc. ), which allow only for qualitative and subjective interpretation of these changes 7,22,27,29,34,[36][37][38][39][40][41][42][43][44][45]47,48 . Only two studies attempted to categorize changes in the color of pupal eyes using standardized color charts, which enabled them to use a larger number of categories.…”

Applications of forensic entomology: overview and update

“…Thus, recent studies provide successfully systematic pupal developmental data of forensically important fly species (based on pupal dissection under stereomicroscope) for the estimation of PMI with recommendation to take mikroskopem stereoskopowym), które mogą być pomocne przy określaniu PMI, zalecając uwzględnienie w analizie czynników zakłócających (np. temperatury otoczenia), aby uniknąć błędów [106,107]. Inni badacze oceniali progresję wieku, analizując diapauzę w trzecim stadium larwalnym.…”

“…Od niedawna stosuje się też mikrotomografię komputerową, która pozwala na wykrywanie wewnętrznych i zewnętrznych zmian morfologicznych gatunku C. vicina w celu dokładnego szacowania wieku osobników w stadiach preimaginalnych [112]. "Dysekcja wirtualna" ma przewagę nad metodą klasyczną; może być również wykonywana in consideration confounding factors (such as environmental temperature) to avoid any error [106,107]. Other researchers thought to overcome the problem of aging during diapausing in the third larval stage.…”