Identifying fly puparia by clearing technique: application to forensic entomology

Abstract

In forensic investigations, immature stages of the fly (egg, larva, or puparia) can be used as entomological evidence at death scenes, not only to estimate the postmortem interval (PMI), analyze toxic substances, and to determine the manner of death but also to indicate the movement of a corpse in homicide cases. Of these immature stages, puparia represent the longest developmental time, which makes them of useful. However, in order for forensic entomologists to use puparia effectively, it is crucial that they are able to accurately identify the species of fly found in a corpse. Typically, these puparia are similar in general appearance, being coarctate and light brown to dark brown in color, which makes identification difficult. In this study, we report on the clearing technique used to pale the integument of fly puparia, thereby allowing observation of the anterior end (second to fourth segments) and the profile of the posterior spiracle, which are important clues for identification. We used puparia of the blowfly, Chrysomya megacephala (F.), as the model species in this experiment. With placement in a 20% potassium hydroxide solution daily and mounting on a clearing medium (Permount(R), New Jersey), the profile of the posterior spiracle could be clearly examined under a light microscope beginning on the fifth day after pupation, and the number of papillae in the anterior spiracle could be counted easily starting from the ninth day. Comparison of morphological features of C. megacephala puparia with those of other blowflies (Chrysomya nigripes [Aubertin], Chrysomya rufifacies [Macquart], Chrysomya villeneuvi [Patton], Lucilia cuprina [Wiedemann], and Hemipyrellia ligurriens [Wiedemann]) and a housefly (Musca domestica L.) revealed that the anterior ends and the profiles of the posterior spiracles had markedly distinguishing characteristics. Morphometric analysis of the length and width of puparia, along with the length of the gaps between the posterior spiracles of seven fly species, displayed differences among them. This provides a key to identifying the puparia of these seven fly species.

Morphology of immature stages of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae) for use in forensic entomology applications

“…ligurriens has a fairly wide distribution in the many countries including the Philippines, China, Japan, Korea, Taiwan, India, Sri Lanka, Thailand, Malaysia (Malaya Borneo), Singapore, Indonesia (Sumatra, Java, Sulawesi, Ambon), New Guinea, and Australia (Kurahashi et al 1997), but information pertaining to aspects of forensic importance of this species is limited (Ishijima 1967;Sukontason et al 2007b). The morphology and fine structure of this species has received little attention in comparison to that of other blow fly genera (e.g., Chrysomya spp.).…”

A review of necrophagous insects colonising human and animal cadavers in south-east Queensland, Australia

“…In the case where T. zealandicus were collected 264 from indoor remains during winter, they had colonised H. 265 ligurriens, collected as 2nd and 3rd instar larvae. A parasitised 266 puparium was retained with the wasps and used for identification 267 of the host species [42]. While the literature describing preferred 268 hosts for T. zealandicus is sparse, H. ligurriens has not been 269 mentioned before as a known host species (S. Voss pers comm).…”

Blow Fly (Diptera: Calliphoridae) in Thailand: Distribution, Morphological Identification and Medical Importance Appraisals

“…Pupa stage: The pupa is mahogany brown to dark brown in color and coarctate and barrel shaped. Morphology of puparium has been studied widely under LM [29] and SEM [30][31][32][33][34][35]. A simply key to identify the puparium of some blow fly species of Thailand was summarized by Sukontason et al [29].…”

“…A simply key to identify the puparium of some blow fly species of Thailand was summarized by Sukontason et al [29]. The main characteristics for identification include body appearance (with or without tubercle), such as the 3 rd thoracic segment to 1 st abdominal segment, distance between right and left posterior spiracles, number of bubble membranes and papillae on the anterior spiracle [29][30][31][32][33][34][35].…”