Diptera (Dryomyzidae, Fanniidae, Muscidae, Piophilidae) Associated With Pig Carcasses in a Forest Habitat of Poland: Sex-Related Patterns of Visitation and Effectiveness of Sampling Methods.

Our knowledge on many necrophilous dipterans was limited for a long time mainly due to taxonomic issues. Therefore, findings on the sex-related associations with pig carcasses in Dryomyzidae, Fanniidae, Muscidae, and Piophilidae are presented. Moreover, the effectiveness of pitfall traps and sweep nets in fly sampling were compared, since the correct method of collecting insects is critical for the development and application of entomological tools for forensic purposes. The trapped numbers of all species differed significantly in respect to both sexes. The sex ratios were strongly female-biased in most species of Muscidae and in Fanniidae. More females were also collected in Piophilidae, but the proportion of males was higher when compared to muscids. Within Dryomyzidae, the sex ratio differed according to species. Only Dryomyza flaveola (Fabricius, 1794) (Diptera: Dryomyzidae) and Muscina pascuorum (Meigen, 1826) (Diptera: Muscidae) had male-biased sex ratios. Differences in residency patterns between sexes in Stearibia nigriceps (Meigen, 1826) (Diptera: Piophilidae), Liopiophila varipes (Meigen, 1830) (Diptera: Piophilidae), and D. flaveola were statistically insignificant. All studied species were recorded for each sampling method. The effect of the sampling method on the number of individuals was statistically significant for all dipterans but Piophilidae. Pitfall traps outcompeted the aerial sweep net in representing Dryomyzidae and Muscidae, whereas both methods were almost equally effective in the collection of Piophilidae. A varied effectiveness of sampling methods was observed in Fanniidae. The sampling method significantly affected the determination of the appearance time of flies on carcasses, but the effect of species and sampling method was insignificant. Implications for forensic entomology are discussed.

DNA Barcoding Identifies Unknown Females and Larvae of Fannia R.-D. (Diptera: Fanniidae) from Carrion Succession Experiment and Case Report.

Application of available keys to European Fanniidae did not facilitate unequivocal species identification for third instar larvae and females of Fannia Robineau-Desvoidy, 1830 collected during a study of arthropod succession on pig carrion. To link these samples to known species, we took the advantage of molecular identification methods and compared newly obtained cytochrome oxidase subunit I (COI) barcode sequences against sequences deposited in reference databases. As an outcome of the results obtained, we describe for the first time a third instar larva of Fannia nigra Malloch, 1910 and Fannia pallitibia (Rondani, 1866) and a female of Fannia collini d'Assis-Fonseca, 1966. We provide combinations of characters allowing for discrimination of described insects from other Fanniidae. We provide an update for the key by Rozkosný et al. 1997, which allows differentiation between females of F. collini and other species of Fanniidae. Additionally, we provide a case of a human cadaver discovered in Southern Poland and insect fauna associated with it as the first report of F. nigra larvae developing on a human body.

A comparative study of the entomofauna (Coleoptera, Diptera) associated with hanging and ground pig carcasses in a forest habitat of Poland.

Suicide by hanging is one of the most common causes of death, worldwide. Therefore, studies of insects associated with hanging cadavers are important for developing entomological tools capable of estimating the postmortem intervals in such cases. We conducted a two-year experiment, in the spring, summer, and autumn of 2012 and 2013, studying the entomofauna of 12 hanging and 12 ground, decomposing pig carcasses in a hornbeam-oak forest, in western Poland. Both carcass treatments showed colonization by similar insect species. Among the 224 taxa collected, 61 and 52 were minimally abundant (≥10 individuals) during the adult stage on at least one hanging and at least one ground carcass, respectively. During the spring and autumn, more adult flies were attracted to hanging carcasses, whereas during the summer, their numbers were similar on both hanging and ground carcasses. Adult beetles were higher in number on hanging carcasses during the spring, but during the summer and autumn, they were slightly more abundant on ground pig carcasses. Irrespective of the carcass treatment, Dryomyzidae, Muscidae, and Piophilidae were the most abundant flies, whereas representatives of Geotrupidae, Histeridae, and Silphidae were the dominant families in the studied beetle community. Only Anoplotrupes stercorosus (Scriba) and Hydrotaea similis Meade adults and Calliphora vomitoria (Linnaeus) larvae reached minimal abundance on all carcasses during all seasons. Carcass treatment only affected the numbers of minimally abundant fly species at the larval stage due to their higher numbers on ground pig carcasses. Although differences in the residency patterns of insects were observed between carcass treatments, they were not significant. In general, adult insects tended to be present for slightly longer times on hanging carcasses than on ground carcasses, whereas beetle larvae had longer presences on ground pig carcasses. Fly larvae were present on ground carcasses for the same amount of time as on hanging carcasses. More broken residency patterns were observed among the adult insects and beetle larvae that colonized hanging carcasses. Fly larvae that colonized ground carcasses had more breaks within the presence periods than fly larvae colonizing hanging carcasses. Neither treatment significantly affected the time of insect appearance on carrion. Most species appeared at the same time or at within one- or two-day intervals on both treatments. Seasonal differences in insect appearance were found, with most species colonizing quickly during the summer. The implications of these findings for forensic entomology are discussed.

Decomposition of hanging pig carcasses in a forest habitat of Poland.

We present the results of the first study on the decomposition of hanging carcasses in a forest habitat of Poland. The decomposition of 12 hanging pigs and 12 ground pigs, which were used as control, in spring, summer, and autumn was examined during a two-year study. Mosaic decomposition was observed with bloating, active decay, and advanced decay irrespective of the carrion treatment (hanging vs ground). Bloating was less visible or did not occur at all in hanging pigs. After undergoing advanced decay, carcasses became mummified and remained in the hanging position. Complete skeletonization was observed only within the head in one case in summer. Irrespective of the carrion treatment, the active decay was driven by the same blow fly species with a similar seasonal pattern of larval dominance. The season was found to affect the decomposition of the hanging carcasses as revealed by a distinct delay in the onset of bloating in autumn and the late onset of active decay in spring. The duration of active decay was the shortest in summer and the longest in autumn. The effect of carrion treatment on the rate of decomposition was statistically insignificant. Nevertheless, some differences in the duration of decomposition between hanging and ground pigs were observed. The most distinct difference was that earlier decomposition proceeded faster in hanging pigs in spring and a delayed decomposition was observed in autumn. In summer, decomposition was similar in all the carcasses. The presented results are largely in contrast to the findings of previous studies on decomposition of hanging pig carrion.

Effect of body mass and clothing on carrion entomofauna.

Carcass mass largely affects pattern and rate of carrion decomposition. Supposedly, it is similarly important for carrion entomofauna; however, most of its likely effects have not been tested experimentally. Here, simultaneous effects of carcass mass and clothing are analyzed. A factorial block experiment with four levels of carcass mass (small carcasses 5-15 kg, medium carcasses 15.1-30 kg, medium/large carcasses 35-50 kg, large carcasses 55-70 kg) and two levels of carcass clothing (clothed and unclothed) was made in a grassland habitat of Western Poland. Pig carcasses (N = 24) were grouped into spring, early summer, and late summer blocks. Insects were sampled manually and with pitfall traps. Results demonstrate that insect assemblages are more complex, abundant, and long-lasting on larger carcasses, whereas clothing is of minor importance in this respect. Only large or medium/large carcasses were colonized by all guilds of carrion insects, while small or medium carcasses revealed high underrepresentation of late-colonizing insects (e.g., Cleridae or Nitidulidae). This finding indicates that carcasses weighing about 23 kg-a standard in forensic decomposition studies-give an incomplete picture of carrion entomofauna. Residencies of all forensically relevant insects were distinctly prolonged on larger carcasses, indicating that cadaver mass is a factor of great importance in this respect. The pre-appearance interval of most taxa was found to be unrelated to mass or clothing of a carcass. Moreover, current results suggest that rate of larval development is higher on smaller carcasses. In conclusion, this study demonstrates that carcass mass is a factor of crucial importance for carrion entomofauna, whereas the importance of clothing is small.

Flesh flies (Diptera: Sarcophagidae) colonising large carcasses in Central Europe.

Sarcophagidae are an important element of carrion insect community. Unfortunately, results on larval and adult Sarcophagidae from forensic carrion studies are virtually absent mostly due to the taxonomic problems with species identification of females and larvae. The impact of this taxon on decomposition of large carrion has not been reliably evaluated. During several pig carcass studies in Poland, large body of data on adult and larval Sarcophagidae was collected. We determined (1) assemblages of adult flesh flies visiting pig carrion in various habitats, (2) species of flesh flies which breed in pig carcasses, and (3) temporal distribution of flesh fly larvae during decomposition. Due to species identification of complete material, including larvae, females, and males, it was possible for the first time to reliably answer several questions related to the role of Sarcophagidae in decomposition of large carrion and hence define their forensic importance. Fifteen species of flesh flies were found to visit pig carcasses, with higher diversity and abundance in grasslands as compared to forests. Sex ratio biased towards females was observed only for Sarcophaga argyrostoma, S. caerulescens, S. similis and S. carnaria species group. Gravid females and larvae were collected only in the case of S. argyrostoma, S. caerulescens, S. melanura and S. similis. Sarcophaga caerulescens and S. similis bred regularly in carcasses, while S. argyrostoma was recorded only occasionally. First instar larvae of flesh flies were recorded on carrion earlier or concurrently with first instar larvae of blowflies. Third instar larvae of S. caerulescens were usually observed before the appearance of the third instar blowfly larvae. These results contest the view that flesh flies colonise carcasses later than blowflies. Sarcophaga caerulescens is designated as a good candidate for a broad forensic use in Central European cases.

Insects colonising carcasses in open and forest habitats of Central Europe: search for indicators of corpse relocation.

Several traces may reveal the post-mortem relocation of a corpse. Insects are particularly useful for that purpose. The use of insects for inferring the transfer of a corpse rests on a premise that particular species colonise corpses in different habitats. However, only some insects reveal a strong preference for a given type of habitat. In order to find those insects which colonise corpses exclusively in open habitats, as opposed to forest habitats, a pig carrion study was made in rural open and rural forest habitats of Central Europe. Lucilia sericata (Diptera: Calliphoridae), Dermestes frischi, Dermestes laniarius (Coleoptera: Dermestidae), Omosita colon, some species of Nitidula (Coleoptera: Nitidulidae) and Necrobia rufipes (Coleoptera: Cleridae) were found to breed exclusively in open habitats. Only Oiceoptoma thoracicum (Coleoptera: Silphidae) avoided definitely breeding in open habitats. Sarcophaga caerulescens (Diptera: Sarcophagidae) regularly bred in open habitats but rarely bred in forests. Accordingly, L. sericata, D. frischi, O. colon, species of Nitidula and supposedly N. rufipes may be classified as indicators of corpse relocation from rural open to rural forest habitats of Central Europe. Only O. thoracicum may be classified as an indicator of the relocation in an opposite direction.