Faeces feeding by adult Phormia regina (Diptera: Calliphoridae): impact on reproduction

Characterization of insect stains produced by Dermestes maculatus De Greer (Coleoptera: Dermestidae) resulting from interactions with human blood

Insect stains produced by adult Dermestes maculatus were characterized during interactions with human blood. Beetles were offered wet or dried blood positioned on ceramic tiles under laboratory conditions. Despite a life history strategy geared toward consumption of dried food stuffs, adult beetles interacted with wet blood more frequently than dried and produced more insect stains after ingesting wet blood. Most (> 95%) of the insect stains produced were the result of fecal elimination. These stains varied in morphologies but were consistently tan/light, black/grey, or red in color; were round to amorphous in shape; and frequently possessed tails. Tailed stains typically were tadpole-shaped or long and tapering from the stain body, yielding Ltl/Lb ratios greater than 1. Tails were the result of beetle locomotion while defecating. Human blood was detected in defecatory stains when using ABA Hematrace® lateral flow assays. When beetles interacted with dried blood, the bloodstains were most often modified due to physical disruption rather than feeding activity. This yielded flaking or dislodgement of the original stains. Within a forensic context, it is unknown whether D. maculatus interacts with any type of bloodstains at a crime scene.

Synanthropic Flies-A Review Including How They Obtain Nutrients, along with Pathogens, Store Them in the Crop and Mechanisms of Transmission

An attempt has been made to provide a broad review of synanthropic flies and, not just a survey of their involvement in human pathogen transmission. It also emphasizes that the crop organ of calliphorids, sarcophagids, and muscids was an evolutionary development and has served and assisted non-blood feeding flies in obtaining food, as well as pathogens, prior to the origin of humans. Insects are believed to be present on earth about 400 million years ago (MYA). Thus, prior to the origin of primates, there was adequate time for these flies to become associated with various animals and to serve as important transmitters of pathogens associated with them prior to the advent of early hominids and modern humans. Through the process of fly crop regurgitation, numerous pathogens are still readily being made available to primates and other animals. Several studies using invertebrate-derived DNA = iDNA meta-techniques have been able to identify, not only the source the fly had fed on, but also if it had fed on their feces or the animal's body fluids. Since these flies are known to feed on both vertebrate fluids (i.e., from wounds, saliva, mucus, or tears), as well as those of other animals, and their feces, identification of the reservoir host, amplification hosts, and associated pathogens is essential in identifying emerging infectious diseases. New molecular tools, along with a focus on the crop, and what is in it, should provide a better understanding and development of whether these flies are involved in emerging infectious diseases. If so, epidemiological models in the future might be better at predicting future epidemics or pandemics.

Pollinator nutrition and its role in merging the dual objectives of pollinator health and optimal crop production

Bee and non-bee insect pollinators play an integral role in the quantity and quality of production for many food crops, yet there is growing evidence that nutritional challenges to pollinators in agricultural landscapes are an important factor in the reduction of pollinator populations worldwide. Schemes to enhance crop pollinator health have historically focused on floral resource plantings aimed at increasing pollinator abundance and diversity by providing more foraging opportunities for bees. These efforts have demonstrated that improvements in bee diversity and abundance are achievable; however, goals of increasing crop pollination outcomes via these interventions are not consistently met. To support pollinator health and crop pollination outcomes in tandem, habitat enhancements must be tailored to meet the life-history needs of specific crop pollinators, including non-bees. This will require greater understanding of the nutritional demands of these taxa together with the supply of floral and non-floral food resources and how these interact in cropping environments. Understanding the mechanisms underlying crop pollination and pollinator health in unison across a range of taxa is clearly a win–win for industry and conservation, yet achievement of these goals will require new knowledge and novel, targeted methods.

This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.

Insects as Chemical Sensors: Detection of Chemical Warfare Agent Simulants and Hydrolysis Products in the Blow Fly Using LC-MS/MS

In this work, blow flies were investigated as environmental chemical sample collectors following a chemical warfare attack (CWA). Blow flies sample the environment as they search for water and food sources and can be trapped from kilometers away using baited traps. Three species of blow flies were exposed to CWA simulants to determine the persistence and detectability of these compounds under varying environmental conditions. A liquid chromatography mass spectrometry (LC-MS/MS) method was developed to detect CWA simulants and hydrolysis products from fly guts. Flies were exposed to the CWA simulants dimethyl methylphosphonate and diethyl phosphoramidate as well as the pesticide dichlorvos, followed by treatment-dependent temperature and humidity conditions. Flies were sacrificed at intervals within a 14 day postexposure period. Fly guts were extracted and analyzed with the LC-MS/MS method. The amount of CWA simulant in fly guts decreased with time following exposure but were detectable 14 days following exposure, giving a long window of detectability. In addition to the analysis of CWA simulants, isopropyl methylphosphonic acid, the hydrolysis product of sarin, was also detected in blow flies 14 days post exposure. This work demonstrates the potential to obtain valuable samples from remote or access-restricted areas without risking lives.

Blow flies, synanthropy and sex ratio: Are the deviations in the sex proportion linked to human transformation of landscapes?

In most species, several factors like time of emergence, age at maturation, reproductive life span, survival of males and females, mating behavior, differential resource use, and migration patterns may affect the adult sex ratio. Anthropogenic landscape transformation is known to change diversity, favoring colonization by exotic species but other populational parameters, such as the sex ratio, have not been assessed. The aim of the present study was to describe the sex-ratio patterns of adult necrophagous blow flies captured using carrion-baited traps along habitats representing different levels of human impact. We describe the sex bias for four species: the exotic Chrysomya albiceps, Chrysomya megacephala, Chrysomya putoria, and the native Cochliomyia macellaria. Three types of habitats were selected: highly anthropized (urbanized), moderately anthropized (rural), and native forest (natural) within a humid subtropical ecoregion in Northeastern Argentina. We found an overall trend to female bias among the four species when considering the total number of each sex. However, our study showed a changing sex-ratio pattern along the gradient of human influence. Our results indicate that a higher likelihood of trapping more males in unsuitable habitats seems to be widespread among blow flies. Urban exploiters, such as Ch. megacephala and Ch. putoria, locally shifted their trends, becoming male-biased in natural habitats. The opposite trend was detected in the urban avoider Co. macellaria (which shifted to male-biased in urban habitats). The exception was Ch. albiceps, whose sex proportion did not shift to a male-biased sex ratio. The results of this study highlight the changing sex-ratio patterns displayed by Calliphoridae in response to different conditions along a human-influence gradient. The biological traits and underlying mechanisms promoting the intraspecific changes of the sex ratio are discussed.

Blow fly stable isotopes reveal larval diet: A case study in community level anthropogenic effects

Response to human impacts on the environment are typically initiated too late to remediate negative consequences. We present the novel use of stable isotope analysis (SIA) of blow flies to determine human influences on vertebrate communities in a range of human-inhabited environments, from a pristine national park to a dense metropolitan area. The refrain "you are what you eat" applies to the dietary isotope record of all living organisms, and for carrion-breeding blow flies, this translates to the type of carcasses present in an environment. Specifically, we show that carnivore carcasses make up a large proportion of the adult fly's prior larval diet, which contrasts to what has been reportedly previously for the wild adult fly diet (which consists of mostly herbivore resources). Additionally, we reveal the potential impact of human food on carcasses that were fed on by blow flies, underscoring the human influences on wild animal populations. Our results demonstrate that using SIA in conjunction with other methods (e.g., DNA analysis of flies) can reveal a comprehensive snapshot of the vertebrate community in a terrestrial ecosystem.

Detection of fly artifacts from four species of necrophagous flies on household materials using immunoassays

An immunoassay was previously developed as a technique to improve methods for detection and analysis of fly artifacts found at crime scenes. The dot blot assay utilized a polyclonal antiserum (anti-md3) based on a unique digestive cathepsin D found in cyclorrhaphous Diptera. In this study, artifacts produced by adults of Calliphora vicina, Cynomya cadaverina, Sarcophaga bullata, and Protophormia terraenovae were examined using the immunoassay to determine if insect-derived stains could be distinguished from a range of human body fluid stains. A lift technique was developed which permitted transfer of fly artifacts from test materials to filter paper for dot blot analyses. All species readily deposited artifacts on all test household materials regardless of diet consumed. Despite differences in texture and porosity of the household materials, artifacts of all species transferred to the filter paper. With all fly species, anti-md3 serum bound to artifacts produced after feeding on semen, blood, feces, urine, and saliva. By contrast, anti-md3 serum did not react with any of the human fluids tested, nor with any of the lifts from household materials not exposed to flies. There was no evidence of false positives with any of the fly species tested, regardless of diet consumed. There was also no indication of false negatives with any of the dot blot assays. These observations suggest that immunoassays using anti-md3 serum performed on a simple lift of suspected fly artifacts can be used effectively as a confirmatory assay to distinguish fly regurgitate and fecal stains from human body fluids.

Female Blow Flies As Vertebrate Resource Indicators

Rapid vertebrate diversity evaluation is invaluable for monitoring changing ecosystems worldwide. Wild blow flies naturally recover DNA and chemical signatures from animal carcasses and feces. We demonstrate the power of blow flies as biodiversity monitors through sampling of flies in three environments with varying human influences: Indianapolis, IN and two national parks (the Great Smoky Mountains and Yellowstone). Dissected fly guts underwent vertebrate DNA sequencing (12S and 16S rRNA genes) and fecal metabolite screening. Integrated Nested Laplace Approximation (INLA) was used to determine the most important abiotic factor influencing fly-derived vertebrate richness. In 720 min total sampling time, 28 vertebrate species were identified, with 42% of flies containing vertebrate resources: 23% DNA, 5% feces, and 14% contained both. The species of blow fly used was not important for vertebrate DNA recovery, however the use of female flies versus male flies directly influenced DNA detection. Temperature was statistically relevant across environments in maximizing vertebrate detection (mean = 0.098, sd = 0.048). This method will empower ecologists to test vertebrate community ecology theories previously out of reach due practical challenges associated with traditional sampling.

Pollinator specialization in the enigmatic Rafflesia cantleyi: A true carrion flower with species-specific and sex-biased blow fly pollinators

The plants of the enigmatic genus Rafflesia are well known for their gigantic flowers and their floral features such as pungent floral scent and vivid dark color, which mimics the food/brood sites of carrion. However, information on the pollination biology of this plant group remains limited and mostly anecdotal. In the present paper, we studied the floral volatiles of R. cantleyi Solms-Laubach and their role in pollinator attraction. To achieve these aims, the floral scent was collected in situ in the field using a dynamic headspace method followed by chemical analysis via GC-MS. The olfactory preferences of pollinators to the identified chemical compounds, were tested singly and in blends, in flight tunnel bioassays and compared with responses to headspace floral extracts. In addition, flower-visiting calliphorid flies and the local carrion fly community were sampled and identified. Five species of calliphorid flies (subfamilies of Chrysomyinae and Calliphorinae), all females, were found on the flowers, whereas nine species were found in the traps that were baited with tainted meat in the surrounding habitat. However, only flower visitors of one blow fly species, Chrysomya chani Kurahashi, were observed to carry R. cantleyi pollen after visiting male flowers. The floral volatiles emitted by male flowers in full bloom were dominated by two sulphur-containing compounds, dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS). These were accompanied by other minor compounds such as benzenoids (4), monoterpenoids (4), trace amounts of aliphatic compounds (1), and sesquiterpenes (1). In flight-tunnel bioassays, a female-specific positive response of C. chani flies to individual DMDS, DMTS, and a blend of DMDS and DMTS was evident. Our findings suggest that R. cantleyi biochemically mimics carrion and that relative ratio of oligosulfides in the floral scent play a key role in sex-biased pollinator specialization, attracting only female C. chani carrion flies to the flowers.

Sex Ratio and Abundance Fluctuations of Sarcosaprophagous Calyptratae (Diptera): Field Evaluation of Two Sampling Techniques

Abundance of sarcosaprophagous Calyptratae species was monitored by using baited traps and active captures with hand net. Analysis of field data collected in three protected areas in the Valdivian temperate forest of South America (Lanín National Park, Lago Puelo National Park, and Los Alerces National Park) indicated that bottle traps baited with putrescine is a reliable method to estimate local abundance of sarcosaprophagous species by comparison to the active capture method. Also, we describe and compare general patterns of sex bias for four dominant species: Sarconesia magellanica (Le Guillou), Calliphora vicina Robineau-Desvoidy, Microcerella spinigena (Rondani), and Oxysarcodexia varia (Walker). From these analyses, it can be concluded that abundance fluctuations of flies showed significant relationship between the sampling methods. This study showed that besides the expected interspecific differences in trapping efficiency, there are acute intraspecific differences of sex ratios between sampling methods.

Effects of Floral Scent, Color and Pollen on Foraging Decisions and Oocyte Development of Common Green Bottle Flies

The common green bottle fly Lucilia sericata (Meigen) and other filth flies frequently visit pollen-rich composite flowers such as the Oxeye daisy, Leucanthemum vulgare Lam. In laboratory experiments with L. sericata, we investigated the effect of generic floral scent and color cues, and of Oxeye daisy-specific cues, on foraging decisions by recently eclosed flies. We also tested the effect of a floral pollen diet with 0–35% moisture content on the ability of females to mature their oocytes. Our data indicate that (1) young flies in the presence of generic floral scent respond more strongly to a uniformly yellow cue than to any other uniform color cue (green, white, black, blue, red) except for ultraviolet (UV); (2) the floral scent of Oxeye daisies enhances the attractiveness of a yellow cue; and (3) moisture-rich pollen provides nutrients that facilitate ovary maturation of flies. With evidence that L. sericata exploits floral cues during foraging, and that pollen can be an alternate protein source to animal feces and carrion, Pollen apparently plays a major role in the foraging ecology of L. sericata and possibly other filth flies. These flies, in turn, may play a significant role as pollinators, as supported by a recently published study.

Lethal and sub-lethal effects of faecal deltamethrin residues on dung-feeding insects

Endectocides administered to livestock to facilitate pest and parasite control may be excreted in the faeces at concentrations that are toxic to coprophagous insects, including species of ecological importance. Although much research has focused on the effects of macrocyclic lactones, relatively less attention has been given to any similar impacts of the widely used pyrethroid insecticides. Here, the effects of faecal residues of the pyrethroid deltamethrin after application to Holstein-Friesian cattle in a proprietary pour-on formulation are examined. Freshly dropped dung was collected 1, 3, 5 and 7 days after treatment and from an untreated control group. In laboratory bioasssays, female Lucilia sericata (Diptera: Calliphoridae) blow flies matured significantly smaller egg batches and had a lower percentage of eggs hatch after feeding on dung collected for up to 5 days after treatment, compared with flies feeding on dung from untreated cattle. In the field, artificial dung pats were constructed from the collected dung and left on pastureland for 7 days before being retrieved and searched for insects. Significantly more adult Diptera emerged from the faeces of untreated cattle than from the dung of treated cattle collected on days 1 and 3 after treatment. Adult Coleoptera were found in lower numbers in the dung of treated animals compared with control dung, suggesting a repellent effect. The results indicate that deltamethrin residues in cattle faeces have a range of lethal and sub-lethal effects on dung-feeding insects for up to a week after treatment, but that the precise duration and nature of toxicity varies depending on the sensitivity of the insect in question.

Sex-biased Patterns of Saprophagous Calyptratae (Diptera) Collected With Different Baits of Animal Origin

The aim of the present study was to explore the response behavior of males and females of different families of Calyptratae (Diptera) to two different baits (rotten liver and feces) as separate attractants. We describe the sex bias toward these baits for species of Calliphoridae, Muscidae, and Sarcophagidae and compare the general patterns of this sex bias according to the family or trophic guild. In total, 15 species of Sarcophagidae, 10 species of Muscidae, and 9 species of Calliphoridae were analyzed. A female-biased pattern was observed for most calliphorids and for all muscids, whereas a male-biased pattern was more frequent among sarcophagids. The female captures on each kind of bait were assessed as a potential indicator of potential breeding substrates of the species. Three different trophic guilds and their pattern of sex bias were compared. The results obtained allow hypothesizing on the biological traits of saprophagous species, especially on their potential breeding substrates, and assessing proper sampling methods.

Spatial characterization of proteolytic enzyme activity in the foregut region of the adult necrophagous fly, Protophormia terraenovae

The spatial distribution of proteolytic enzymes in the adult foregut of Protophormia terraenovae was studied in the context of protein digestion and regurgitation. Based on substrate specificity, pH optima, and use of specific protease inhibitors, all adults tested displayed enzyme activity in the foregut consistent with pepsin, trypsin and chymotrypsin. Chymotrypsin-like and trypsin-like enzyme activity were detected in all gut fluids and tissues tested, with chymotrypsin displaying the highest activity in saliva and salivary gland tissue, whereas maximal trypsin activity was evident in the crop. Pepsin-like activity was only evident in crop fluids and tissues. The activity of all three enzymes was low or undetectable (pepsin) in the fluids and tissue homogenates derived from the esophagus and cardia of any of the adults assayed. Fed adult females displayed higher enzyme activities than fed males, and the activity of all three enzymes were much more prevalent in fed adults than starved. The pH optimum of the trypsin-like enzyme was between pH 7.0 and 8.0; chymotrypsin was near pH 8.0; and maximal pepsin-like activity occurred between pH 1.0 and 2.0. Regurgitate from fed adult females displayed enzyme activity consistent with the proteolytic enzymes detected in crop gut fluids. Enzymes in regurgitate were not derived from food sources based on assays of bovine liver samples. These latter observations suggest that adult flies release fluids from foregut when encountering dry foods, potentially as a means to initiate extra-oral digestion.

Decomposed flesh as a vitellogenic protein source for the forensically important Lucilia sericata (Diptera: Calliphoridae)

For the carrion-feeding blow flies, a common source of vitellogenic protein are the carcasses that also serve as larval substrates. This attraction continues well after the blow flies have ceased to oviposit on the carrion, and it has been assumed that a decomposed cadaver remains a suitable source for vitellogenic protein; however, this assumption has never been tested. To test this hypothesis, blow flies (Lucilia sericata Meigen) were supplied with either fresh or decomposed beef liver as protein sources for vitellogenesis for 5 d. Both treatments produced identical ovarian development, indicating that decomposed flesh remains a suitable protein source for carrion-feeding blow flies. These results support the theory that virgin flies are attracted to cadavers of advanced decomposition as a source of protein.

Annual and spatial activity of dung flies and carrion in a Mediterranean holm-oak pasture ecosystem

The annual activity and spatial distribution of Muscidae and Calliphoridae were investigated in a holm-oak ('dehesa') ecosystem in western Spain over two years in pasture and woodland habitats, using wind-orientated traps baited with a mixture of fresh cattle faeces, liver and sodium sulphide solution. Lucilia sericata (Meigen) was always the dominant species and, with Chrysomya albiceps (Weidemann), Hydrotaea ignava (Harris), Muscina levida (Harris) and Muscina prolapsa (Harris), was more abundant during the second than the first year. By contrast, Calliphora vicina Robineau-Desvoidy, Calliphora vomitoria (L.), Hydrotaea armipes (Fallén), Hydrotaea penicillata (Rondani) and Hydrotaea dentipes (Fabricius) were more numerous during the first than the second year of the study. In summer, the Diptera sampled were significantly more abundant in a wooded than a pasture area. However, in autumn, while H. penicillata remained significantly more abundant in woodland, L. sericata became more abundant in the pasture, whereas C. vicina was captured in open and wooded areas in similar proportions. During winter and spring the populations sampled were relatively small. The changing patterns of abundance are discussed in relation to differences in climate within and between years.