Luisa M. Díaz-Aranda

The distribution of adult blow-flies (Diptera: Calliphoridae) along an altitudinal gradient in Central Spain

Abstract The distribution of Calliphoridae along an altitudinal gradient was investigated in Central Spain using carrion-baited traps. Significant differences were found between elevation and mean abundances of almost all species of blow-flies. Several species of flies could be grouped according to their altitudinal preferences so that samples at high elevations are defined by Calliphora vomitoria and Calliphora vicina while samples at low elevations are defined by two thermophilous species: Lucilia sericata and Chrysomya albiceps. The remaining species show preferences for mid-elevations where wooded areas are more characteristic along the altitudinal gradient. Calliphora vomitoria and Chrysomya albiceps are the most abundant species representing the 87.74 % of all captures. Both species are spatially segregated along the altitudinal gradient. The changing patterns of abundance are discussed in relation to differences in climate conditions along the altitudinal gradient concluding that the environmental variables that influence the seasonality of many species also play an important role to explain the spatial distribution.

Preliminary data on carrion insects in urban (indoor and outdoor) and periurban environments in central Spain

Although most cases involving entomological evidence occur in urban environments and under indoor conditions, there is a lack of studies determining the insect fauna of forensic importance in those environments. In the current paper we provide the first data on the composition of the forensically important insect species occurring in periurban and both indoor and outdoor urban environments in central Spain. Insects were collected fortnightly by means of carrion-baited traps, uninterruptedly during one year. Most species and individuals were collected in the periurban site, whereas the indoor urban site showed the lowest number of species and captures. Moreover, the composition of species differed among environments and seasons. A few species occurred under both indoor and outdoor conditions, including the blowfly Calliphora vicina and some Sarcophagidae species. These preliminary results suggest interesting differences in the insect composition between environments and conditions which may be of forensic importance, and represent a first step to further research into the application of insects to forensic investigations in urban environments of central Spain.

The immature stages of the necrophagous fly, Prochyliza nigrimana : comparison with Piophila casei and medicolegal considerations (Diptera: Piophilidae)

Flies of family Piophilidae have been recorded as major pests in the food industry, as agents of human myiasis and typically associated with carcasses in advanced stages of decay, being thus important in forensic entomology. Despite that the cosmopolitan species Piophila casei is the most cited in entomological studies, many other piophilid species develop on both carrion and animal products from the food industry. One of those species is Prochyliza nigrimana, widely distributed throughout the Holarctic and Neotropical regions. In this study, the morphological features of the immature stages of P. nigrimana are described for the first time and compared with those of P. casei. The third-instar larvae and puparium of P. nigrimana are significantly shorter than those of P. casei; the contrary pattern is observed in egg length. The number and arrangement of the lobes of anterior spiracles, which had been used as a distinctive character of P. casei in some keys, are the same in both species. Morphological features of the cephaloskeleton (such as the general shape and the distance between the tips and the base of the mouth hooks/base of the mouth hooks ratio), the arrangement of anal segment in third-instar larvae and the appearance of the ventral creeping welts in the puparium are the main characters allowing for identification of both species.

Early colonisation of urban indoor carcasses by blow flies (Diptera: Calliphoridae): An experimental study from central Spain

Due to their ubiquity and synanthropy, blow flies (Diptera: Calliphoridae) are generally the first colonisers of cadavers and, therefore, frequently used to estimate a minimum post-mortem interval (minPMI). Whereas in outdoor situations blow flies are expected to locate and colonise exposed cadavers within hours or even minutes after death, it is usually assumed that the colonisation of a cadaver indoors might be delayed for an uncertain period of time. This uncertainty severely limits the informativity of minPMI estimates based on entomological evidence. Moreover, these limitations are emphasised by the lack of experimental data on insect colonisation of indoor carrion and by the fact that most of the forensic cases involving entomological evidence have been reported to occur indoors. In this study we investigate the early colonisation of pig carcasses placed indoors in a building located in the centre of an urban environment in central Spain. Three carcasses were placed in three equal rooms with a window half opened during five experimental trials: summer 2013, autumn 2013, winter 2014, spring 2014 and summer 2014. The species composition and their contribution to the carrion colonisation differed among seasons. Calliphora vicina Robineau-Desvoidy was the sole coloniser of carcasses in winter and colonised the carcasses within the first 24-48h in every season, although Lucilia sericata (Meigen) was the first coloniser of most summer carcasses. On the other hand, Calliphora vomitoria (L.) and Chrysomya albiceps (Wiedemann) colonised the carcasses significantly later in spring and in spring and summer, respectively, with a delay of several days. In autumn, however, there were no significant differences in the colonisation times by C. vicina, L. sericata and Ch. albiceps. C. vicina and L. sericata showed a clear preference for ovipositing in the natural orifices of the carcasses, whereas Ch. albiceps oviposited more frequently on the trunk and legs.

Effect of Temperature on the Survival and Development of Three Forensically Relevant Dermestes Species (Coleoptera: Dermestidae)

Abstract Most Dermestes species (Coleoptera: Dermestidae) are scavengers during both larval and adult stages, with a preference for dry organic matter. Because of this, Dermestes beetles are potentially useful indicators in forensic investigations concerning skeletonized and mummified human remains. However, there is a paucity of reference developmental data on most forensically relevant Dermestes species. This study analyses the effect of five constant temperatures (15, 20, 25, 30, and 35 °C) on the survival and developmental rates of three of the forensically most relevant dermestids: Dermestes frischii Kugelan, Dermestes maculatus De Geer, and Dermestes undulatus Brahm. Pig skin was used as rearing substrate, to use a substrate as similar as possible to that exploited in nature. Overall, the temperature had a significant effect on the survival and the duration of development, with optimal values at intermediate temperatures. Both D. frischii and D. maculatus showed similar developmental rates and the shortest developmental times at 30 °C, whereas D. undulatus developed faster at lower temperatures. At 15 °C, both D. frischii and D. undulatus did not oviposit, whereas no D. maculatus individuals survived beyond the pupal stage. An inconsistent number of larval instars per individual were observed across different constant temperatures in the three species. The present study aims to provide baseline developmental data for further advances in the potential use of Dermestes beetles as forensic tools in long postmortem interval cases.

Necrophilous Histerid Beetle Communities (Coleoptera: Histeridae) in Central Spain: Species Composition and Habitat Preferences

ABSTRACT Despite the applied importance of necrophilous histerid beetles, their communities and habitat preferences had not been characterized in the Iberian Peninsula. The current article describes the composition of those communities in seven types of natural habitats along a bioclimatical gradient in central Spain, describing and discussing the habitat preferences and niche breadths of the most abundant species. In total, 25 species of necrophilous Histeridae were collected using carrion-baited traps. As a result, six groups of species can be distinguished according to their habitat preferences. These groupings depend on either the distribution among habitats or their restriction to certain habitats. Moreover, within each habitat, the type of vegetation was a factor structuring histerid communities, with those species with wide distribution throughout several habitats showing a preference for more open areas.

Annual variation in decomposition and insect succession at a periurban area of central Iberian Peninsula

The variation in decomposition and insect succession among the four seasons of one year was studied for the first time in a periurban area of central Spain. During the winter trial, the carcasses showed corification, a cadaveric preservation phenomenon which apparently leaded to a significant delay in decomposition processes. The composition of the insect fauna breeding on carcasses changed significantly between trials. Active decay was mainly driven by Calliphoridae (Diptera) larvae in every season except in winter trial, when larvae of Thanatophilus species (Coleoptera: Silphidae) were the main consumers of soft tissues. Advanced decay was characterized by the occurrence of Dermestidae, Silphidae, Cleridae, Nitidulidae (Coleoptera) and Piophilidae (Diptera) larvae. Differences in the species composition in comparison with other regions of the Iberian Peninsula were also observed. The current paper provides baseline and preliminary information on the insect succession on carrion in central Spain, as well as a starting point for further research on forensic entomology in this region.

Environmental correlates of species diversity for sarcosaprophagous Diptera across a pronounced elevational gradient in central Spain

Abstract Measuring the biological diversity in a given area can provide valuable approaches not only to conserve ecological systems, but also to understand their functioning and organization. The current paper analyzes the species richness and diversity patterns of sarcosaprophagous Diptera across an elevational gradient of natural habitats in central Spain, and the relationship between the species diversity and the environmental variables defining each habitat. The calculation of randomized species richness curves and non-parametric estimators confirmed the representativeness of the inventories. Oromediterranean habitats, i.e. those located at highest elevation, showed significantly lower species richness than mesomediterranean and supramediterranean levels. Slope and solar radiation were significantly and negatively correlated with diversity, whereas the correlation between mean temperature and diversity was significantly positive. A significantly negative correlation was found between diversity and the percentage of forest surface, whereas the correlation between diversity and the percentage of urban surface was positive and close to significance. Possible explanations for these observed patterns are considered and discussed. This study also supports the use of different, complementary diversity measurements in order to obtain a proper assessment of the diversity of a given area.

Larval identification key to necrophagous Coleoptera of medico-legal importance in the western Palaearctic

Several necrophagous Coleoptera species are frequently collected on cadavers, may occasionally act as intermediate or paratenic hosts of parasites, as vectors of pathogens or as allergens, and can also represent major pests of preserved animal products. However, despite their medical, veterinary and economic importance, there is a lack of reliable species identification tools for the larval stages (usually the only entomological evidence associated with medicolegal investigations), thus severely limiting their potential application as forensic indicators. Here, we provide an identification key to the larvae of the necrophagous Coleoptera species which have been recorded on carrion in the western Palaearctic region, based on easily observable morphological characters. In total, we provide diagnostic characters for the reliable identification of 23 necrophagous Coleoptera species within four different families (Cleridae, Dermestidae, Nitidulidae and Silphidae). In addition to the aforementioned families, we provide diagnostic characters for the identification of the larvae of families Histeridae, Staphylinidae and Trogidae, which can also be collected on cadavers. It is expected that the present key will facilitate the identification of larval material of necrophagous Coleoptera collected either in carrion succession studies or during medicolegal investigations, in order to further advance in the potential use of this insects as forensic tools.