Evolution of flexible biting in hyperdiverse parasitoid wasps.

One key event in insect evolution was the development of mandibles with two joints, which allowed powerful biting but restricted their movement to a single degree of freedom. These mandibles define the Dicondylia, which constitute over 99% of all extant insect species. It was common doctrine that the dicondylic articulation of chewing mandibles remained unaltered for more than 400 million years. We report highly modified mandibles overcoming the restrictions of a single degree of freedom and hypothesize their major role in insect diversification. These mandibles are defining features of parasitoid chalcid wasps, one of the most species-rich lineages of insects. The shift from powerful chewing to precise cutting likely facilitated adaptations to parasitize hosts hidden in hard substrates, which pose challenges to the emerging wasps. We reveal a crucial step in insect evolution and highlight the importance of comprehensive studies even of putatively well-known systems.

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.

To attach or not to attach? The effect of carrier surface morphology and topography on attachment of phoretic deutonymphs of Uropoda orbicularis (Acari).

Previous studies on preferences of phoretic deutonymphs of Uropodina for attachment sites have shown that they frequently select smooth and hydrophobic surfaces. The aim of our study was to provide the detailed morphological and topographical characteristics of beetle body surfaces to which deutonymphs frequently attach and to verify how the presence of setae and surface sculpture affects deutonymph attachment. The study was conducted on Uropoda orbicularis (Müller, 1776) and its common beetle carriers: Aphodius prodromus (Brahm, 1790), Aphodius fimetarius (Linnaeus, 1758), Onthophagus nuchicornis (Linnaeus, 1758) and Margarinotus carbonarius (Hoffmann, 1803). Morphology and topography of elytra, femora, propygidia and pygidia of beetles were analysed mainly using SEM methods supported with CLSM and AFM techniques. The hypothesis that deutonymphs may attach to surfaces covered with setae, if seta density is low enough not to disturb mite movement, was tested. The study revealed that deutonymphs attach to surfaces of various types as follows: (i) smooth, (ii) hairy, i.e., covered with setae, (iii) flat and (iv) sculptured. Smooth body parts and body parts covered with setae of low density were most frequently and intensively occupied with deutonymphs. Surfaces of high seta density were avoided by mites. Within elytra of Aphodius beetles, deutonymphs definitely preferred flat surfaces of elytral intervals. On the contrary, densely punctuated propygidium and pygidium in M. carbonarius were heavily infested with deutonymphs. We conclude that carrier surface morphology and topography are important for Uropodina deutonymph attachment, but these two factors cannot fully explain the observed relation.

Localization and density of phoretic deutonymphs of the mite Uropoda orbicularis (Parasitiformes: Mesostigmata) on Aphodius beetles (Aphodiidae) affect pedicel length.

The phoretic stage of Uropodina mites is a deutonymph with developed morphological adaptations for dispersal by insects. Phoretic deutonymphs are able to produce a pedicel, a stalk-like temporary attachment structure that connects the mite with the carrier. The aim of our study was to determine whether localization and density of phoretic deutonymphs on the carrier affect pedicel length. The study was conducted on a common phoretic mite--Uropoda orbicularis (Uropodina) and two aphodiid beetles--Aphodius prodromus and Aphodius distinctus. Our results show that pedicel length is influenced by the localization of deutonymphs on the body of the carrier. The longest pedicels are produced by deutonymphs attached to the upper part of elytra, whereas deutonymphs attached to femora and trochanters of the third pair of legs and the apex of elytra construct the shortest pedicels. In general, deutonymphs attached to more exposed parts of the carrier produce longer pedicels, whereas shorter pedicels are produced when deutonymphs are fixed to non-exposed parts of the carrier. A second factor influencing pedicel length is the density of attached deutonymphs. Mean pedicel length and deutonymph densities were highly correlated: higher deutonymph density leads to the formation of longer pedicels. The cause for this correlation is discussed, and we conclude that pedicel length variability can increase successful dispersal.

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.

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.

Morphological diversity of pedicels in phoretic deutonymphs of Uropodina mites (Acari: Mesostigmata).

The pedicel is a structure that connects the phoretic deutonymph of Uropodina mites with its carrier and enables dispersal. The shapes, lengths and diameters of pedicels formed by Uropoda orbicularis, Trichouropoda ovalis, Uroobovella pulchella and Uroobovella nova were studied by scanning and light microscopy. Pedicels of U. orbicularis and T. ovalis have the shape of a straight stalk. In U. pulchella, the pedicel is extremely short, irregularly shaped and composed of homogeneous material. The longest pedicel is found in U. nova and it may be helically coiled in this species. The length of the pedicel is positively correlated with deutonymph body size between species, but not within species. Pedicels of U. orbicularis and U. pulchella have the largest diameter. The pedicel diameter in U. orbicularis and T. ovalis is inversely proportional to its length, but not in U. nova and U. pulchella. The constituent of pedicel stems in U. pulchella is homogeneous, whereas in U. orbicularis and T. ovalis it contains a bundle of tightly packed fibres. In U. nova coiled pedicels are comprised of two layered materials of different electron density, one of which is electron lucid and located peripherally. Hypotheses on the origin of the pedicel are proposed.

Anatomy and fine structure of pedicellar glands in phoretic deutonymphs of uropodid mites (Acari: Mesostigmata).

Phoretic deutonymphs of uropodid mites are attached to their carrier via an anal pedicel which is formed by a secretion from the pedicellar gland. Since the ultrastructure of the pedicel and pedicellar gland has never been investigated, we studied these structures in three species, Uropoda orbicularis (Müller), Uroobovella marginata (Koch), and Trichouropoda ovalis (Koch) by light (LM) and electron microscopy (TEM, SEM). In addition, the pedicel in Uroobovella nova (Oudemans) was documented in SEM. The pedicellar gland is a distinct globular structure comprised of three types of secretory cells (A-, B-, and C-types) with apical parts directed towards a junctional zone of postcolon and anal atrium. Secretory cells of the A-type are located dorsally, whereas B-type cells are central, and C-type cells are distributed ventrally or both ventrally and dorsally. Protrusions of visceral muscle cells are distributed on the external surface of the gland. The cuticle-lined anal atrium is large and located between the gland and dorso-anal muscles. The pedicel is composed of a main stalk and two extended extremities: one adhering to the anal region of the deutonymph and a second connected to the cuticle of the carrier. In each case, the anal atria were empty, whereas the pedicellar material was located outside of the mite body.

Insect succession and carrion decomposition in selected forests of Central Europe. Part 3: Succession of carrion fauna.

The succession of insects on pig carrion was monitored in spring, summer and autumn, in three forest types and 2 years in Western Poland (Central Europe). In most forensically useful taxa, significant differences between seasons, forests and years in time of appearance on carrion were found. The lowest values of appearance time were recorded in summer and the highest in spring. In alder forest insects appeared on carcasses significantly earlier than in pine-oak forest and hornbeam-oak forest. In summer periods of insect presence on carrion were significantly shorter than in spring and autumn. In most taxa no significant effect of forest type or year on length of the presence period was found. In all seasons assemblages of adult taxa were clearly more aggregated than assemblages of larval taxa. Sequence of insects' appearance on carcasses was very similar in different seasons, forests and years. General seasonal models of insect succession on carrion are proposed for forests of Central Europe. Data on appearance time and length of the presence period in particular seasons, forests and years are presented for forensically useful taxa. Implications for methods of PMI estimation (particularly the succession-based method) are discussed.

Insect succession and carrion decomposition in selected forests of Central Europe. Part 1: Pattern and rate of decomposition.

Pig carrion decomposition and insect succession were monitored in different seasons and forests of Central Europe. Pattern of decomposition as well as onset, duration and rate of decompositional processes were measured. Pattern of decomposition was the same in almost all cases with putrefaction, active and advanced decay. In the majority of carcasses active decay was driven by larvae of Calliphoridae with a clear seasonal shift in dominant taxa. However, in some spring, alder forest cases active decay was driven by larvae of Necrodes littoralis (Coleoptera: Silphidae). As a rule the mosaic decomposition was observed. In spring a significant delay in onset of all decompositional processes was found. Season significantly affected rate of active decay due to a much higher rate in summer. Decomposition in alder forest proceeded faster than in pine-oak forest and hornbeam-oak forest. Differences between the latter two forests were practically negligible. Implications for forensic entomology are discussed.

Insect succession and carrion decomposition in selected forests of Central Europe. Part 2: Composition and residency patterns of carrion fauna.

The insect fauna of pig carcasses was monitored in different seasons and forests of Western Poland (Central Europe). The composition of carrion fauna and selected features of residency in carrion in adults and larvae of particular taxa were analysed. A total of 131 adult and 36 larval necrophilous taxa were collected. Only 51 adult species and 24 larval taxa were minimally abundant (>or=10 specimens) at least on one carcass. As for the composition of carrion fauna, there were large differences between seasons, but no important differences between forest types. In most species of Diptera, length of the presence period of adults was between 35 and 65% of the sampling interval, while in most species of Coleoptera, it was above 60%. Only in a few species (e.g., Saprinus semistriatus, Necrodes littoralis or Creophilus maxillosus) was the presence period shorter than 35% of the sampling interval. Interestingly, in some adult Coleoptera (e.g., Necrobia violacea) very long presence periods were recorded. In most taxa, the length of the presence period of larvae was between 40 and 65% of the sampling interval. Only Calliphora vomitoria, Phormia regina, Hydrotaea dentipes, N. littoralis and C. maxillosus had shorter presence periods of larvae. As a rule, residency of adults was broken, whereas residency of larvae was unbroken. Moreover, in adults, two distinct residency patterns were observed; with breaks clumped in the final part of the presence period and with breaks evenly distributed inside the presence period. Almost in all taxa, the time of appearance showed the closest relationship to the onset of bloating. The relationship was significant, positive and strong in adults of P. regina, Fannia manicata, Hydrotaea ignava, Stearibia nigriceps, S. semistriatus, N. littoralis and C. maxillosus as well as larvae of P. regina, H. dentipes, H. ignava, S. nigriceps, N. littoralis, Oiceoptoma thoracicum, Thanatophilus sp., C. maxillosus and Philonthus sp. Interestingly, in some forensically significant taxa (e.g., adults of N. violacea or Thanatophilus rugosus), we found no significant relationship between the time of their appearance and the onset of any decompositional process. Implications for the succession-based post-mortem interval (PMI) estimation, determination of the carcass movement and the season of death are discussed.

An initial study of insect succession and carrion decomposition in various forest habitats of Central Europe.

At the end of summer and beginning of fall 2005 insect succession and pig carrion decomposition were studied in pine-oak forest, hornbeam-oak forest, and alder forest in Western Poland (Central Europe). Five stages of decomposition were recognized: fresh stage, bloated stage, active decay stage, advanced decay stage, and remains stage. The highest rate of decomposition was observed in the alder forest and the lowest in the pine-oak forest. A similar composition of carrion entomofauna was found in each forest. Numerous adults of Lucilia caesar, Phormia regina and Calliphora vomitoria (Calliphoridae), Hydrotaea spp. (Muscidae), Stearibia nigriceps and Parapiophila vulgaris (Piophilidae), Necrodes littoralis and Thanatophilus rugosus (Silphidae), Creophilus maxillosus, Omalium rivulare, Oxypoda acuminata and Philonthus spp. (Staphylinidae) as well as larvae of L. caesar, P. regina, C. vomitoria, Fannidae (Diptera) and N. littoralis, C. maxillosus, Philonthus (Coleoptera) were collected. There were no differences between forests in the sequence of insect occurrence on carrion. However, differences between forests in occurrence time and activity period of some taxa were found. Implications of these results for forensic entomology are discussed.