Urban and Rural Spatial Delineations in Blow Fly Species (Diptera: Calliphoridae) Across Canada: Implications for Forensic Entomology

Spatio-Temporal Influence on the Distribution of Forensically Relevant Blowflies (Diptera: Calliphoridae) in Gyeongsangnam-do, South Korea

The study of blowfly (Diptera: Calliphoridae) biodiversity and distribution is crucial for forensic investigations. Abiotic and biotic factors, such as season and habitat type, have a significant impact on blowfly populations. However, only a few forensic entomology studies have been conducted in South Korea, particularly in the Gyeongsangnam-do region. To address this, an extensive year-long survey was conducted to analyze the compositions, habitat preferences, distribution, and seasonal abundance of forensically relevant blowflies in urban and forested habitats of Gyeongsangnam-do, with sampling conducted twice a month using mouse carcass-baited traps set for 48 h each time. A total of 3470 adult blowflies were recorded, encompassing five genera and 13 species, with a noted absence of specimens during the winter months. The predominant species was Lucilia porphyrina, accounting for 37.2% of the total sample, followed by Chrysomya pinguis (27.6%), Lucilia sericata (7.6%), and Lucilia illustris (7.1%). The species composition was consistent across all surveyed regions; however, seasonal variation in species diversity was evident, with a peak in spring and a decline in summer. Notably, certain species exhibited clear preferences for either urban (Calliphora calliphoroides and L. sericata) or forested habitats (L. porphyrina and Ch. pinguis). This pioneering study elucidates the diverse blowfly communities in Gyeongsangnam-do, highlighting significant seasonal and habitat-dependent variations. These findings enrich our understanding of blowfly ecology in this region, offering valuable insights for forensic applications and underscoring the necessity for ongoing entomological surveillance and research.

Development of Phormia regina at seven constant temperatures for minimum postmortem interval estimation

Phormia regina (Meigen, 1826) (Diptera: Calliphoridae) can colonize carcasses quickly, and its immature stages are reliable entomological evidence for the estimation of the minimum postmortem interval (PMImin). There are discrepancies in the developmental data from previous studies on P. regina, and the related PMImin indicators need to be refined. We investigated the accuracy of forensic entomological evidence using development durations, growth accumulated degree hours, and larval body length variations of P. regina at seven constant temperatures ranging from 16 to 34 °C. We also established development models such as the isomorphen diagram, thermal summation model, isomegalen diagram, and body length simulation equation to assist with PMImin estimation. The developmental duration of P. regina from egg to adult at 16, 19, 22, 25, 28, 31, and 34 °C was 840.8 ± 42.8 h, 580.1 ± 10.1 h, 390.4 ± 8.7 h, 316.8 ± 9.4 h, 291.4 ± 21.2 h, 238.4 ± 2.8 h, and 222.5 ± 5.2 h, respectively. The lower threshold temperature TL was 9.97 ± 0.50 °C, while the thermal constant K was 5052.7 ± 229 degree days. The lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold obtained by the Optim SSI models were 13.15, 21.20, and 36.86 °C, respectively. This study aims to provide developmental models for P. regina aimed at common case-site temperatures in the northern provinces of China, which can be used for accurate PMImin estimation.

Decomposition and insect succession on human cadavers in a humid, continental (Dfb) climate (Quebec, Canada)

Forensic entomology has been developing globally for decades. Despite this discipline being used in criminal investigations around the world, only a few controlled studies have been performed on human cadavers in human decomposition facilities, with the majority of these being conducted in warm and often dry climates. Therefore, the purpose of our research was to catalogue the first published data on insects associated with decomposed human bodies in a humid, continental (Dfb) climate. Specifically, our objective was to document the diversity and succession of the entomofauna associated with human cadavers throughout the decomposition process, in the Quebec province of Canada, during the summer season. Two human cadavers were studied in 2020 at the site for Research in Experimental and Social Thanatology, REST, located in Bécancour (Quebec, Canada). Insects (and other arthropods) were regularly sampled by visual observations, collection from the cadavers, and by using an entomological net and pitfall traps. Our results highlight that the decomposition process is a heterogeneous and complex process in Quebec, with cadavers showing signs of precocious desiccation/mummification. In addition, our observations confirm that the presence of superficial skin lesions accelerates the colonization of blow flies (Diptera: Calliphoridae) and, consequently, the process of decomposition. Finally, we were able to discriminate between "early colonizers" (e.g., Calliphoridae Lucilia sp. or Calliphora livida), "late colonizers" (e.g., larvae of Piophilidae or Heleomyzidae), and "non-specific colonizers." We also officially report the first observation of Cochliomyia macellaria (Diptera: Calliphoridae) in Quebec. These findings will provide new information to help medico-legal death investigations by determining the minimum time elapsed since death and the circumstances surrounding death.

Domestic Filth Flies in New Haven, Connecticut: A Case Study on the Effects of Urbanization and Climate Change by Comparing Fly Populations after 78 Years

Simple Summary

Domestic filth fly population data were collected in the summers of 1942–1944 in the urban city of New Haven, Connecticut, during a polio epidemic. The current survey was completed 78 years later by setting out a weekly trap in the same region during June–September over a two-year period. Results indicate that the fly population has changed in the city, with 16 fewer species trapped overall, and there have been changes in the fly species trapped. Some species have increased in abundance, notably Lucilia coeruleiviridis, while numbers of the common Lucilia sericata have decreased, and Lucilia illustris was absent. Changes in land cover and climate were also assessed to show that the trap site has experienced significant habitat change, together with an increase in the average temperature and rainfall. Fly numbers were significantly affected by temperature and rainfall in both the 1940s and the current survey. The results of this study suggest the prolonged period of urbanization of the region is influencing the domestic filth fly population.

Abstract

Changes in common and widespread insect populations such as the domestic filth fly in urban cities are useful and relevant bioindicators for overall changes in the insect biomass. The current study surveyed necrophagous flies by placing a weekly trap from June–September over a two-year period in the city of New Haven, Connecticut, to compare data on fly abundance and diversity with data collected 78 years earlier. Climate and land cover changes were also assessed in combination with the fly population for each period. The survey results suggest the domestic filth fly population is now less diverse with decreased species richness and changes in the relative abundance of species. In both surveys, 95–96% of the population was composed of only three species. The current survey data indicate the numerical dominance of Lucilia sericata has decreased, the abundance of several species, notably Lucilia coeruleiviridis, has increased, and Lucilia illustris is absent. Species that showed a significant interaction with temperature in the 1940s survey have now increased in abundance, with several of the trapped species continuing to show an interaction with temperature and rainfall. Analysis of the land cover and climate data characterizes the trap site as a region exposed to a prolonged period of industrialization and urbanization, with only 7% of the land cover remaining undeveloped and over 50% impervious, coupled with an increase in temperature and rainfall. This study serves as a model for changes in domestic filth fly populations and other insects in similarly highly urbanized established cities.

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.

Ignatzschineria indica bloodstream infection associated with maggot infestation of a wound in a patient from Canada

We describe a case of Ignatzschineria indica bacteremia in a patient with maggot infestation of a necrotic left leg wound. Ignatzschineria spp are an infrequent cause of infection in patients with wound myiasis. We review 16 cases described in published literature. Microbiologists and clinicians should be aware of uncommon bacteria, including Ignatzschineria spp, that may cause infection in patients with maggot-infested wounds such that these organisms are appropriately worked up and treated when found in clinical specimens.

Adult Blow Fly (Diptera: Calliphoridae) Community Structure Across Urban-Rural Landscapes in Michigan, United States

Necrophagous insects play an important role in the decomposition of vertebrate carrion. The documented colonization, development, and succession of blow flies (Diptera: Calliphoridae) and other arthropods on decomposing carcasses make their communities relevant for use in decomposition ecology and forensic investigations. This relevance relies on the local pool of species available to colonize a carcass, but such community level survey data are not always available. The objective of this research was to conduct a baseline survey of adult Calliphoridae communities from urban-rural land use types in the Great Lakes region. To test how adult blow fly distribution varies with changing landscape in Mid-Michigan, sampling with baited jars and hanging traps was implemented over the summer months of June, July, and August 2017. To determine how blow fly communities differed in urban to rural land cover, seven cities were selected with site locations ranging from high intensity developed areas to cultivated crop fields. Over 97,000 individual flies were captured represented by 11 Calliphoridae species. The adult Calliphoridae communities were primarily structured by land use type and month of collection, with these two factors interacting, suggesting that the effect of location varied by time of year. The two most abundant species, Phormia regina (Meigen) and Lucilia sericata (Meigen), cumulatively comprised 88.5% adult flies from Mid-Michigan. These findings provide a baseline database of Great Lakes Calliphoridae, with potential use in forensic research and casework.

Bridging the gap between academia and practice: Perspectives from two large-scale and niche research projects in Canada

There is a recognized disconnect in priority and synergy between academic and practitioners in forensic science. In this work, we personally reflect on our experiences in conducting research studies that directly involve academic and practitioner stakeholders. We believe, amongst others, that this "gap" can be mitigated through regular and productive communication. We also emphasize the need to create stronger and national research strategies which identifies the current and pressing needs of enforcement officials in order to bring these needs directly to academia. As part of this, researchers should actively seek to make sure what they study will be relevant within the discipline. Our reflection is geared on direct feedback from an entomological study in large scale sampling of blowflies and workshops in bloodstain pattern analysis using a forensic blood substitute.