Larval morphology of the lesser housefly, Fannia canicularis

Larval morphology and temperature-dependent development models of Fannia pusio (Wiedemann): a forensic indicator with expanding distribution

Fannia pusio (Wiedemann) is originally from tropical and subtropical regions of the Americas, where it has repeatedly been collected from both animal carrion and human cadavers. This species is expanding its distributional range, and it has been introduced to Africa, Asia, Australia, Oceania, and Europe. Newly introduced species may be confused with native species of local arthropod necrophagous assemblages, which from a forensic entomology perspective may impact the accuracy of post-mortem interval (PMI) estimations based on insect evidence. In this work we aim to raise awareness among forensic entomologists of the potential benefits and risks associated with the expanding range of F. pusio. Morphology of all larval instars is documented with a combination of light, confocal laser scanning and scanning electron microscopy. Characters allowing identification from other forensically important Fanniidae are listed. Thermal requirements for the development of immature stages of F. pusio were examined under nine ambient temperatures. Models describing changes in larval body length over time were produced for eight different temperatures. The thermal summation constant (k) and developmental zero (T_min) were calculated for six developmental events: hatching, first ecdysis, second ecdysis, wandering, pupariation, and eclosion.

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

Simple Summary

Insects are frequently attracted to animal and human cadavers, usually in large numbers. The practice of forensic entomology can utilize information regarding the identity and characteristics of insect assemblages on dead organisms to determine the time elapsed since death occurred. However, for insects to be used for forensic applications it is essential that species are identified correctly. Imprecise identification not only affects the forensic utility of insects but also results in an incomplete image of necrophagous entomofauna in general. The present state of knowledge on morphological diversity and taxonomy of necrophagous insects is still incomplete and identification of immature and female forms can be extremely difficult. In this study, we utilized molecular identification methods to link conspecific sexes and developmental stages of forensically important flies. We identified larvae and females of flies collected from animal and human cadavers which otherwise were morphologically unidentifiable. The present study fills a gap in taxonomy of flies and provides data facilitating application of new species as forensic indicators.

Abstract

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 Rozkošný 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.

First description of the immature stages of Fannia sabroskyi Seago, 1954 (Insecta, Diptera, Fanniidae)

Egg, larvae and the puparium of Fannia sabroskyi Seago, 1954 (Diptera, Fanniidae) are described and illustrated for the first time. The following structures have been documented: pseudocephalon, antennal complex, maxillary palpus, facial mask, anterior spiracle, cephaloskeleton structures, thoracic and abdominal processes, anal division, and posterior spiracle. Due to its necrophagous habit, this species may be of potential forensic importance for estimating the postmortem interval in criminal investigations. The information presented herein may be useful to distinguish the immature forms of Fannia species and to supplement the database for identification of Neotropical species of Fanniidae. In addition, it is also important for evolutionary and phylogenetic studies.

Thermal requirements for the development of immature stages of Fannia canicularis (Linnaeus) (Diptera: Fanniidae)

Entomological material may be used to estimate the time since death occurred (minimum post-mortem interval, mPMI) in forensically obscure cases. The method commonly used to calculate mPMI is the application of a thermal summation model. Little is known about the thermal requirements of Fanniidae. To fill this gap, the influence of temperature on the development time of Fannia canicularis (Linnaeus), a cosmopolitan species with the potential to be used in forensic entomology, was studied. An experiment was performed under nine ambient temperatures. The thermal summation constants (k) and developmental zeros (T_min) of this species were calculated for six developmental events: hatching, first ecdysis, second ecdysis, wandering, pupariation, and eclosion. Data were primarily analysed with two linear models, and then, since the relationship between temperature and development rate is curvilinear close to the lower and higher developmental thresholds, the relationship was also modelled using three nonlinear models. A fourth nonlinear model was also used to estimate the intrinsic optimum temperature of F. canicularis, at which the population size is maximal and the mortality is the lowest. At 33 °C, larvae did not hatch from eggs, and thus changes in larval body length were analysed at the eight remaining temperatures. Fannia canicularis development from egg to eclosion required a mean ± SE of 481.73 ± 9.89 degree-days above a lower threshold temperature of 4.64 ± 0.19 °C. At the lowest experimental temperature tested, 10 °C, F. canicularis successfully completed all developmental events, although ca. 30% of wandering larvae proceeded to the inactive stage instead of pupariation. Results obtained from nonlinear models were not satisfactory and did not allow us to consider them as reliable from a biological point of view.

Morphology and development rate of the immature stages of Glyphidops (Oncopsia) flavifrons (Bigot, 1886) (Diptera, Neriidae) under natural conditions

Of the 116 Neriidae species known to date, 113 species have not been studied in their immature stages. Here, we examine the development of the immature stages of Glyphidops (Oncopsia) flavifrons (Bigot, 1886), which has one of the broadest distributions of Neriidae in southern North America, Central America, and South America; offering excellent opportunities for biological studies. A population of this species was monitored over a five month period. The following characteristics were tracked for a population located on the University of Valle campus in Cali, Colombia: oviposition duration, number of eggs per egg mass and lifespan of each immature stage (egg, larva, and puparium) under natural conditions (in situ). The external morphology of the egg, larva, and puparium were described; their stages lasted 58 (± 4) hours, 10 (± 1) days and 13 (± 1) days, respectively. The lapse of time for each larval instar was statistically supported by using Tukey comparisons and cluster analysis of hypopharyngeal sclerite length and mandibular area. In addition, it was also sustained throughout the morphological study of structural changes in mouth hook, and anterior and posterior spiracles. Finally, the presence of the labial and epipharyngeal sclerites are reported as new characters of Nerioidea. Natural history data are provided.

Fanniidae (Diptera): new synonym, new records and an updated key to males of European species of Fannia

Based on revision of large recent collections of the authors, the following five species are first recorded from the Czech Republic: Fannia collini d'Assis-Fonseca, 1966 (simultaneously first record in Central Europe), Fannia lugubrina (Zetterstedt, 1838), Fannia melania (Dufour, 1839), Fannia slovaca Gregor & Rozkošný, 2005, and Fannia brinae Albuquerque, 1951 (simultaneously first record from low altitudes). Another species, Fannia alpina Pont, 1970, is first recorded from Slovak Republic, and Fannia cothurnata (Loew, 1873) is first recorded from Kazakhstan. An updated key to males of European species of Fannia is presented. A list of Czech and Slovak Fanniidae is appended. One new synonym is established: Fannia lucida Chillcott, 1961 is considered junior synonym of Fannia norvegica Ringdahl, 1934. Altogether two species are first recorded from Bohemia [Fannia cothurnata (Loew, 1873) and Fannia vespertilionis Ringdahl, 1934] and three for Moravia [Fannia alpina Pont, 1970, Fannia conspecta Rudzinski, 2003, and Fannia limbata (Tiensuu, 1938) - this species considered in Central Europe very rare was found in numbers near waters both running and standing in early spring under unusually warm temperature conditions].

Morphology of the first instar larva of obligatory traumatic myiasis agents (Diptera: Calliphoridae, Sarcophagidae)

There are only three fly species that are obligate agents of traumatic myiasis of humans and livestock: a single species of flesh fly, Wohlfahrtia magnifica (Sarcophagidae), and two species of blow flies, Chrysomya bezziana and Cochliomyia hominivorax (Calliphoridae). The morphology of their first instar larvae is thoroughly and consistently documented here with light microscopy photographs and scanning electron microscopy micrographs. The following morphological structures are documented: pseudocephalon, antennal complex, maxillary palpus, oral ridges, thoracic and abdominal spinulation, spiracular field, posterior spiracles and cephaloskeleton. New diagnostic features drawn from the cephaloskeleton and the spinulation of abdominal segments, including the anal pad, are discovered and extensively described. Earlier descriptions in the literature are revisited, and major discrepancies between these and the results of the current study are discussed. The present results allow clarification, correction and, especially, complementation of information provided by earlier authors. The relatively distant taxonomic position of all three species is evidence that obligatory myiasis has arisen independently, and the extensively similar morphology in the first instar larvae of Chrysomya bezziana, Cochliomyia hominivorax and W. magnifica in comparison to necrophagous species, especially the enhancement of the anterior part of the cephaloskeleton and the segmental spinulation, is therefore best interpreted as homoplasic adaptations to a life strategy as obligate vertebrate parasites. An identification key for first instar larvae of all obligatory traumatic myiasis agents of mammals is provided.

Ultrastructure of preimaginal stages of Piophila megastigmata McAlpine, 1978 (Diptera, Piophilidae): a fly of forensic importance

Piophila Fallén, 1810 is a genus of small flies composed of two species: Piophila casei (P. casei ) (Linnaeus, 1758), worldwide distributed, and Piophila megastigmata (P. megastigmata ) McAlpine, 1978, recently referred in the Palaearctic Region, from the Iberian Peninsula. Both species share ecological niche and are very interesting for forensic purposes, since they are present in carrion in advance stages of decay and have been found to be related to human corpses. The immature stages of P. megastigmata have ever been described, so this paper gives the ultrastructural morphologies of all preimaginal stages of P. megastigmata studied by light microscopy and scanning electron microscopy (SEM). Particular attention is given to pseudocephalon features—antenna, maxillary palps, facial mask, etc.—cephalopharyngeal skeleton, anterior and posterior spiracles, tegumentary sculpturing, and anal division among others. A comparative analysis of the main distinguishing features is made in order to understand how those features evolve along the developmental process, while larvae II and III are morphologically similar to each other, the larva I shows particular features. Larvae of all stages and pupae are easily distinguishable from other Diptera of forensic importance just based on the presence of trichoid sensilla associated to respiratory slits, instead of peristigmatig tufts, as well as on thewell-known disposition of anal papillae. The shapes of both dorsal edge at the basal part of mouthhook and dorsal bridge of cephalopharyngeal skeleton, and the tegumental ornamentationmay be considered as good features to distinguish the Piophila species, especially for P. megastigmata and P. casei . At the SEM level, shape, number, and arrangement of oral combs, oral ridges, sensilla of maxillary palpus, papillae of anterior spiracle, scales of spiracular field, and posterior spiracles represent good features to distinguish P. megastigmata from P. casei, but further studies will be necessary in West-Paleartic specimens of latter species. The key for identifying third instar larvae of forensically important Piophilidae in the Iberian Peninsula has been updated to include P. megastigmata.

Larval morphology, development and forensic importance of Synthesiomyia nudiseta (Diptera: Muscidae) in Europe: a rare species or just overlooked?

The muscid Synthesiomyia nudiseta (van der Wulp, 1883) is a species with forensic importance in tropical and subtropical regions of the world. This fly has recently been introduced into southern Europe and, until now, had not been recorded in forensic cases in this region. Here, morphology of all larval instars of S. nudiseta is documented in detail by using a combination of light and scanning electron microscopy. Literature data concerning larval morphology are revised and characters allowing identification from other forensically important Muscidae are listed. The life cycle of this species was studied at four constant temperatures: 15, 20, 25 and 30 °C. Total development varied between 46.50 ± 0.97 days at 15 °C and 15.39 ± 0.32 days at 30 °C. Moreover, we report this species breeding in human corpses, for the first time in Europe, in forensic cases from autopsies at the Anatomical Forensic Institute of Madrid and the Institute of Legal Medicine of Alicante, Spain.