Comparing Species Composition of Passive Trapping of Adult Flies with Larval Collections from the Body during Scene-Based Medicolegal Death Investigations

Biodiversity of Forensically Relevant Blowflies (Diptera: Calliphoridae) at the Anthropology Research Facility in Knoxville, Tennessee, USA

Understanding the biodiversity and distribution of forensically relevant blowflies (Diptera: Calliphoridae) in a region can aid in legal investigations when insects are associated with remains. For this purpose, we conducted a 14-month-long blowfly survey at the Anthropology Research Facility (ARF) of the University of Tennessee in Knoxville, Tennessee. Traps baited with pork kidney were deployed for 24 h twice a month throughout the study. A total of 3180 adult blowflies were collected, comprising 13 species from 7 genera. Phormia regina (Meigen) and Lucilia coeruleiviridis (Macquart) were the predominant species collected from this survey, with collections representing 65.9% and 20.6%of total flies captured, respectively. In addition to relative abundance, we investigated blowfly community composition, species abundance, richness, and diversity by season. One state record was identified, with adult Protophormia terraenovae (Robineau-Desvoidy) being collected for the first time in Tennessee. Additionally, an earlier record of Chrysomya megacephala (Fabricius) in Tennessee was noted. These findings can be used to aid in legal investigations in the area and surrounding areas where work is limited, as well as to provide information on which forensically relevant species should be the subject of future research in the area.

Forensically relevant blow flies (Diptera: Calliphoridae) of Central Connecticut, USA

Connecticut and the Northeastern United States in general, lacks forensically relevant entomological survey data. To determine which forensically relevant calliphorid (blow flies, Diptera: Calliphoridae) and non-calliphorid species dominate Connecticut, 5 traps using pork bait were set out 7 times over a 2-year period to collect adult and immature specimens. Insects collected from human corpses in this region were also tabulated to collaborate the forensic relevance of trapped specimens. The survey identified a total of 8 species of blow flies of the Lucilia and Calliphora genera, 6 of which colonized the baits, and 5 of which have been found to colonize human corpses in the area. Non-calliphorid genera Sarcophaga and Muscina were also found to be colonizers of the baited traps but in relatively lower numbers. Trap sites differed significantly in the degree of urbanization which was determined by using GIS mapping to classify a 1 kilometer (km) radius around each site using land use and the percent of urban impervious surfaces. The 1 km radius revealed the highly fragmented nature of the immediate habitats of the trap sites and no habitat or seasonal preference was demonstrated by blow flies under these trap conditions. Temperature was the one variable which significantly affected the number of flies trapped and the colonizing species. All trapped species have been described previously as widespread and common in the United States and as synanthropic. Further research in this region should trap at the constantly changing extreme ends of the urban-rural gradient and in the colder temperatures of winter to explore the limits of the flexibility of these blow fly species.

The Relationship between Research and Casework in Forensic Entomology

Simple Summary

Forensic entomology concerns the use of insects as evidence in legal investigations. Many sorts of investigation can benefit from an interpretation of insects associated with the crime scene, but insect evidence is most frequently used in investigations of death. The interpretation of insect evidence in casework is guided by the data supplied through research. Such data are essential to improve the casework interpretation of insect evidence, thereby improving the robustness of the legal systems in which it operates. This paper explores the mutually beneficial relationship between research and casework in forensic entomology, contrasting the different challenges that each presents and giving examples of how each can support the other in delivering results of real societal benefit. It is written from the perspective of the Criminal Justice System of England and Wales, but many of the points raised are relevant to legal systems worldwide.

Abstract

Research is a vital component of all forensic sciences and is often stimulated by casework, which identifies gaps in our knowledge. In such a niche area of forensic science as entomology there should be a close and mutually beneficial relationship between research and casework: to some extent there is a continuum between the two and many forensic entomologists are involved in both to a greater or lesser degree. However, research and casework involve quite differing challenges, from the replicated, highly controlled, sometimes esoteric aspects of research to the very individual, sometimes chaotic and disruptive, but highly applied aspects of casework. Ideally casework will include the full involvement of a forensic entomologist, who will collect the insect and climate evidence at the scene and produce a robust expert witness statement based on a full analysis of this data. Unfortunately, it can also include situations where samples, if collected at all, are poorly preserved, not representative of the full cadaver fauna available and presented to the entomologist months or years after the event, without local temperature data. While research is recognised through publications and their citation indices, casework and its associated expert witness statements often receive no credit in an academic workplace, although they do have a positive societal impact and many other benefits of teaching and public engagement value. This manuscript examines the relationship between research and casework from a UK perspective, to raise awareness of the need to create an environment that values the contribution of both, for future generations to flourish in both areas.

An Analysis of Forensically Important Insects Associated with Human Remains in Indiana, U.S.A

Research documenting insect colonization of human remains is limited in North America, and currently nonexistent for the American Midwest. Such research is essential for forensic entomologists to identify species of research interest in a region. In this study, we collected insects from human remains in 24 cases across Indiana from June 2016 through September 2018. We analyzed species composition across scene type and season. Eight species of blow flies were collected as larvae from human remains, with Phormia regina and Lucilia sericata as the two predominant colonizers. Phormia regina was the most numerous species collected from outdoor scenes (73.6% of total collections) while L. sericata was the most numerous from the indoor scenes (60.4% of total collections). With scene types pooled, Calliphora vicina and Cochliomya macellaria were the predominant species in the fall (55.6% and 42.2%, respectively); P. regina was the dominant colonizer in the spring (68.6%); and P. regina and L. sericata were the predominant colonizers (46.5% and 44.4%, respectively) in the summer. In addition to these findings, we confirmed the first record of Lucilia cuprina colonizing human remains in Indiana having collected this species from three cases. A single adult Chrysomya megacephala was collected from an indoor scene in southern Indiana, which represents its second collection in the state. Beetles belonging to the families Staphylinidae, Silphidae, Histeridae, Cleridae, Trogidae, Dermestdae, and Nitidulidae were also collected from two outdoor scenes. This study provides important baseline data for forensic entomologists in Indiana, as well as surrounding states with similar environments.

Development and Field Evaluation of a Novel, Inexpensive Passive Trap for Monitoring Dispersal of Necrophagous Dipteran Larvae

Techniques for the survey of necrophagous dipterans are frequently designed for adult flies and often neglect forensically important information, such as the postfeeding larval dispersal following carcass colonization. In this study, we propose and test a novel trap design for the collection of dipteran larvae at the postfeeding stage. The Trap for Dispersing Larvae (TDL) consists of two semiindependent parts: 1) a 2-liter PET bottle, containing the attractant (carcass); and 2) a plastic box, which selectively captures postfeeding dispersing larvae. Based on a field test in a dry forest fragment in Brazil, the TDL trap captured ca. 1,500 larvae of 13 species of Calliphoridae, Muscidae, Fanniidae, and Sarcophagidae. The species richness of dispersing larvae recorded in our study was ca. 60% of that previously recorded in this area. As the TDL trap can assess larval dispersal without interfering with carcass decomposition, we demonstrate that it can be used to assess temporal variation in the dynamics of colonization. In the present study, most larval dispersal occurred at 5-d postexposure, but the traps remained efficient until 7 d, by which time rat carcasses had skeletonized. We conclude that the TDL trap captures the dispersing dipteran larvae with little interference in carcass decomposition processes. The trap also provides a representative sample of species and is simple to use and of low cost.

Dipteran Attraction to a Variety of Baits: Implications for Trapping Studies as a Tool for Establishing Seasonal Presence of Significant Species

Monitoring and collection of fly taxa (Diptera: Calliphoridae; Muscidae; Sarcophagidae) of medical, veterinary, and agricultural importance is often routine practice, providing data on target species presence, distribution and abundance. Collection practices currently involve baited trapping and while an inherent bias accompanying the choice of bait is acknowledged, there is little consistency in bait choice between studies and insufficient assessment of trapping success rates for bait types in current use. This study aimed to examine the effect of bait choice on trapping results for six commonly used bait types; a commercial bait (Envirosafe Fly Attractant, Envirosafe Products) and a combination of mixtures of liver, horse manure and 5% sodium sulfide (Na2S). Trapping success was compared under different seasonal conditions (Summer, Autumn, and Spring) to determine the most attractive bait for calliphorid species, with a secondary comparison of kangaroo versus ox liver occurring under summer conditions. Baits containing Na2S were the most successful in captures of all target taxa, with the addition of manure desirable, yielding increased diversity of taxa. Kangaroo liver baits attracted high numbers of Chrysomya spp. (Robineau-Desvoidy, Diptera: Calliphoridae), while Lucilia spp. (Robineau-Desvoidy, Diptera: Calliphoridae) were comparatively underrepresented in traps using liver alone. The use of a combined ox liver/manure/Na2S bait is recommended as the gold standard for generic screening of necrophagous flies. Where more specific target fly taxa are desired, such as Chrysomya spp. or Lucilia spp. only, alternate baits such as kangaroo or lamb may prove more attractive/successful.