Decomposition and dipteran succession in pig carrion in central Argentina: ecological aspects and their importance in forensic science

Data on the insect species associated with corpse decomposition are particularly important for estimation of the post-mortem interval (PMI) in forensic science because the PMI is based on the lifecycle and behaviour of necrophagous insects, among other measures. To determine the dipteran succession on pig carrion, four experiments, one in each season, were carried out during 2004 in a rural area of Córdoba, central Argentina. Two pigs ( Sus scrofa L.) were used in each of the four experiments. At each time-point one pig was placed in the shade and the other under direct sunlight. Insects were collected daily during the first 4 weeks and thereafter every 2 or 3 days. Five stages of decomposition were observed and a total of 24 710 adult specimens were collected, belonging to the following eight families of Diptera: Calliphoridae; Muscidae; Sarcophagidae; Phoridae; Piophilidae; Fanniidae; Sphaeroceridae, and Anthomyiidae. All Calliphoridae collected in this study were considered to be of potential forensic importance because of their necrophagous behaviour and because their immature stages use carrion as a food source. Other species, such as Musca domestica L. and Ophyra aenescens (Wiedemann), were also considered to represent potential forensic indicators.     

Effects of carrion decomposition on litter arthropod assemblages

1. Many organisms contribute to the decomposition of carrion. For arthropods, many studies focus on the necrophagous community, those directly consuming carrion.
2. Necrophagous arthropods use carrion as a shelter or food source. Therefore, carrion generally increases the abundance and biodiversity of necrophagous species. However, it is unclear if carrion has similar effects on detrital communities.
3. This study examines changes in community structure and composition of necrophilous and detrital communities over the course of decomposition.
4. Five pig head carrion were placed at least 7 m apart under cages in temperate mixed forest. Leaf litter was sampled 0 m, 1.5 m, and 3 m from each carrion weekly during summer, and monthly during autumn, until the first frost. Arthropods were extracted from leaf litter by using Berlese funnels.
5. At the carrion site, necrophagous insects increased in abundance, species richness, and Shannon diversity during decomposition, and all decreased after dry decay.
6. Detritus arthropods displayed a sharp increase in abundance during advanced decay, decreasing during dry decay, and a general increase over time for species richness and diversity.
7. In conclusion, carrion can influence the surrounding, non-necrophagous arthropod community, highlighting the need to investigate carrion effects beyond typical necrophagous species to have a more holistic understanding of carrion ecology.

     

Insects Associated with Pig Carrion in Two Environments of the Brazilian Savanna

Studies of carrion fauna have increased in Brazil and have contributed to the knowledge of this fauna in the national territory. Brazil has continental dimensions and presents various biomes in its territorial area. Most of the carrion fauna have seldom been studied, and this is especially true for the Savanna or “Cerrado.” The present research examined the fauna visiting carrion in two environments and two seasons in a rural area situated in a region of Cerrado in southeastern Brazil. The two environments studied were a pasture and a fragment of semi-deciduous forest. Samples were collected during the dry and humid seasons of the year. The study identified the diversity and relative abundance of species attracted to pig carcasses (Sus scrofa L.) exposed in each environment and season. Eight pig carcasses (10 ± 1 kg) were placed in traps, and adult insects attracted to the traps were collected during the decay of the carcasses. A total of 92,489 insects were collected during the experiments. The Diptera was the most frequent order (92.2%) represented by 27 families and at least 124 species. This was followed by Coleoptera (4.4%) represented by 14 families and at least 65 species. Sarcophagidae had the greatest diversity of species, followed by Muscidae and Calliphoridae. Several species were collected only during a specific period of the year or in a single environment. The results are important from an ecological point of view and for Medico-Legal Forensic Entomology.     

Beetles succession on different microhabitats of small mammals in Riyadh,Kingdom of Saudi Arabia

The decay of small carcasses is considerably neglected although it may provide important forensic data. This study differentiates the beetle species correlated with rat, Rattus norvegicus and mouse, Mus musculus (L. 1758) carcasses placed in two different habitats at King Saud University in western Riyadh. Decay processes and beetle succession were analyzed from January to February 2018. We collected an average of 268.67 beetles belonging to nine species from eight families, including Histeridae, Dermestidae, Cleridae, Tenebrionidae, Staphylinidae, Coccinellidae, Melolonthinae, and Pyrrhocoridae. Collected specimens were identified morphologically and by molecular techniques based on the mitochondrial cytochrome oxidase subunit I (COI) gene. Their presence rose in the bloated and decaying stages of decomposition. The beetle communities differed between the two habitats. In addition, a distinctive beetle community was found in the decaying stage compared to the other stages. The lowest number of beetles was reported in the dry stage. The abundance of beetles was associated with carcass size (rat or mouse) and habitat type.     

Successional patterns of the insect fauna on a pig carcass in southern Italy and the role of Crematogaster scutellaris (Hymenoptera,Formicidae) as a carrion invader

The sarcosaprophagous fauna plays a key role in organic matter decomposition. Moreover, the biological, ecological and behavioral specificities of the taxa are useful to reconstruct the decay history of a corpse or carcass, often back to the lethal event. Here we report the seasonal succession of the insect fauna on a pig carcass exposed in a rural area in Calabria (southern Italy) during summer 2007 and 2008. The aim is to identify and qualitatively assess the major taxa of forensic importance in this region. The principal fly invaders were Lucilia caesar (L.), L. sericata (Meigen, 1826), Chrysomya albiceps (Wiedemann, 1819), Sarcophaga (Meigen, 1826) spp. and Amobia (Robineau‐Desvoidy, 1830) spp., Musca domestica (L.) and Muscina stabulans (Fallen, 1817). The primary beetle species collected in summer belonged to Dermestidae, Dermestes maculatus (De Geer, 1774) and Cleridae, Necrobia rufipes (De Geer, 1775). This paper also examined the ecological role of ants in the insect succession and describes the evidence of skin injuries directly inflicted by the acrobat ant Crematogaster (Acrocoelia) scutellaris (Olivier, 1791) (Hymenoptera Formicidae) while feeding on pig carrion. Ants belonging to two other species were also collected: Camponotus aethiops (Latreille, 1798) and Tetramorium semilaeve (André, 1881). Ants can invade carcasses and corpses directly, disrupting blowfly egg laying or preying on their larvae. Our data on the carrion faunal composition and role of ants as invaders should be useful for further forensic cases in Calabria (southern Italy). This is among the few reports of ants as forensically relevant species.     

Beetles and flies collected on pig carrion in an experimental setting in Thuringia and their forensic implications

Decomposition processes and insect succession were analysed on a total of eight pig (Sus scrofa) carcasses. The survey was carried out in four different periods between November 2007 and August 2008 and on two different substrates (meadow, concrete floor close to a building). The experiments were placed in a rural site in the surroundings of Jena, Thuringia. The duration and specificity of the different decomposition stages were dependent on season, weather and quality and quantity of insect colonization. Whereas the carrion maintained a bloated appearance even after 133 days in winter, it reached the dry stage within 8 days in the summer months. The type of substrate had few effects on the decaying process, but the insects were generally more abundant on the meadow. In total, more than 57 species of Diptera belonging to 17 families and 48 species of Coleoptera belonging to 14 families were identified. Dominant species belonged to the families of Calliphoridae (n = 11 spp.), Sarcophagidae (n = 8), Muscidae (n = 9), Piophilidae (n = 3), Silphidae (n = 6), Dermestidae (n = 3), Nitidulidae (n = 4), Cleridae (n = 3) and Histeridae (n = 2). Remarkably, the rather common Nicrophorus species were completely absent, whereas the usually rare Necrodes littoralis (L.) was present in larger numbers. No distinct coincidence between the occurrence of a single species and a certain decomposition stage could be confirmed. A main objective of the study is the establishment of a forensic entomological database for Central Europe, especially Thuringia.     

Response of rove beetles (Staphylinidae) to various habitat types and change in Southern Mexico

We evaluated changes in levels of diversity of copro-necrophilous staphylinids attracted to piles of cattle dung and rat carrion in four contrasting habitats (continuous oak forest, oak forest patches, savannah and ravines) in southeastern Mexico during 2005 and 2006. In total, 181 morpho-species (N = 9,875 individuals) of Staphylinidae were recorded, of which 40 were coprophiles, 98 were necrophiles, and 43 were present in both substrates. Ten species accounted for 65% of the total number of individuals, 68 species were represented by singletons, whereas 103 species registered intermediate abundances. Less disturbed habitats recorded higher levels of beetle diversity. A strong seasonality effect was recorded for necrophiles, but not for coprophiles. A beta diversity analysis suggested that continuous oak forest registered the lowest fauna similarity when contrasted to other habitats; yet beetle composition among oak forest patches, savannah and ravine remained comparable. Staphylinidae body size and trophic guilds differed significantly among habitats. The results of this study suggest that key habitats such as ravines may represent a more permanent and predictable habitat for beetles in highly seasonal landscapes, even at early stages, because this habitat is characterized by a slower turnover of Staphylinidae species than in the case of tropical oak patches or savannah habitats.     

Modeling flight activity and population dynamics of the pine engraver, Ips pini, in the Great Lakes region: effects of weather and predators over short time scales

Ascertaining the relative effects of factors such as weather and predation on population dynamics, and determining the time scales on which they operate, is important to our understanding of basic ecology and pest management. In this study, we sampled the pine engraver Ips pini (Say) (Coleoptera: Scolytidae) and its predominant predators Thanasimus dubius (F.) (Coleoptera: Cleridae) and Platysoma cylindrica (Paykull) (Coleoptera: Histeridae) in red pine plantations in Wisconsin, USA, over 2 years. We sampled both the prey and predators using flight traps baited with the synthetic aggregation pheromone of I. pini. Flight models were constructed using weather variables (temperature and precipitation), counts of bark beetles and their predators, and temporal variables to incorporate possible effects of seasonality. The number of I. pini per weekly collection period was temperature dependent and decreased with the number of predators, specifically T. dubius in 2001 and P. cylindrica in 2002. The number of predators captured each week was also weather dependent. The predators had similar seasonal phenologies, and the number of each predator species was positively correlated with the other. Including a term for the number of prey did not improve the model fits for either predator for either year. Our results suggest that exogenous weather factors strongly affect the flight activity of I. pini, but that its abundance is also affected by direct density-dependent processes acting over weekly time scales. Adult predation during both colonization and dispersal are likely processes yielding these dynamics.     

Diptera and Coleoptera of potential forensic importance in southeastern Brazil: relative abundance and seasonality

Abstract. To determine the species of Diptera and Coleoptera that visit and breed in carrion, four experiments, one for each season, were conducted from November 1992 to October 1993 in the vicinity of Campinas city, Southeastern Brazil. For each experiment two pigs weighing c. 10 kg were killed with a blow to the head with a blunt metallic object and immediately exposed, one in the shade and the other under sunlight. Adult insects and larvae leaving the carcass to pupate were collected daily. In addition, female blowflies were dissected in order to determine the stage of ovarian development. Five species of Calliphoridae: Chrysomya albiceps, C.megacephala, C.putoria, Phaenicia eximia and Hemilucilia segmentaria; three of Sarcophagidae: Pattonella intermutans, Liopygia ruficornis and Adiscochaeta ingens , and three of beetles: Dermestes maculatus, D. peruvianus (Dermestidae) and Necrobia rufipes (Cleridae), were considered of potential forensic importance, for they were able to breed in carrion exposed to natural environmental conditions. In addition, several fly species showed a definite seasonal pattern, with the Calliphoridae breeding more frequently during the warmer months of the year, and the Sarcophagidae preferring the cooler periods.     

Selected beetle assemblages captured in pitfall traps baited with deer dung or meat in balsam fir and sugar maple forests of central Quebec

Vertebrate dung and carrion are rich and strongly attractive resources for numerous beetles that are often closely linked to them. The presence and abundance of beetles exploiting such resources are influenced by various ecological factors including climate and forest cover vegetation. We studied selected assemblages of coprophilous and necrophagous beetles in Quebec along a 115-km north-south transect in three balsam fir (Abies balsamea (L.) Miller) forest sites and in a fourth forest site dominated by sugar maple (Acer saccharum Marshall), close to the southern fir site. Beetle abundance was estimated using a sampling design comprising replicated pitfall traps baited with red deer meat or dung in each site. A total of 8,511 beetles were caught and identified to family level, 95.7% of which belonged to families with known coprophilous or necrophagous behavior. Meat-baited pitfall traps caught nearly 15 times as many beetles as dung-baited traps. All Histeridae, Hydrophilidae, Scarabaeidae, and Silphidae were identified to species to examine specific diversity variation among sites. For the beetles caught in the meat-baited traps (majority of captures), decreases in abundance and species richness were observed from south to north along the fir forest transect, with evidence of decreasing specific diversity as measured by the Shannon index of diversity. Strong differences in species assemblages were also observed between the southern maple and fir forest sites. The Silphidae and Histeridae were more abundant in the maple forest, whereas the Hydrophilidae and Ptilidae were more abundant in the fir forest.     

Carrion flies of forensic interest: a study of seasonal community composition and succession in Lisbon,Portugal

Information on Diptera community, seasonality and successional patterns in every geographical region is fundamental for the use of flies as forensic indicators of time of death. In order to obtain these data from the Lisbon area (Portugal), experiments were conducted during the four seasons of the year, using piglet carcasses as animal models. Five stages were recognized during the decomposition process. The stages, besides visually defined, could be separated taking into account the occurrence and abundance of the specific groups of Diptera collected. In general, the bloated stage recorded higher abundance and species‐richness values. Seventy‐one species were identified, belonging to 39 families, in a total of 20 144 adult Diptera collected. Autumn yielded the highest values of species richness, whereas winter had the lowest. In all seasons of the year, Calliphoridae was the dominant family; Muscidae and Fanniidae were very abundant as well. Calliphora vicina Robineau‐Desvoidy, Calliphora vomitoria (Linnaeus), Chrysomya albiceps (Wiedemann), Lucilia ampullacea Villeneuve, Lucilia caesar (Linnaeus), Lucilia sericata (Meigen) (Calliphoridae), Hydrotaea ignava (Harris), Muscina prolapsa (Harris), Synthesiomyia nudiseta (van der Wulp) (Muscidae), Piophila megastigmata McAlpine, Stearibia nigriceps (Meigen) (Piophilidae) and Nemopoda nitidula (Fallén) (Sepsidae) were revealed to be very important members of the Diptera community collected. The necrophagous behaviour, demonstrated by their immatures, using carrion as a food source makes them useful forensic indicator species. Also of relevance is the presence of Chrysomya megacephala (Fabricius), S. nudiseta and P. megastigmata, foreign species established in the local carrion communities. This study also marks the first record of S. nudiseta in Portugal.     

Effects of pesticides on filth fly predators (Coleoptera: Histeridae, Staphylinidae; Acarina: Macrochelidae, Uropodidae) in caged layer poultry manure

A field study on two caged layer poultry operations assessed whether selected pesticides would affect beneficial predators. Sampling was done three times during the 5-wk period before treatment, 3 d after each of two weekly treatments, and 5-6 times during the 10 wk after the second treatment. Cyromazine (0.1%) applied topically had no detrimental effect on any of the predator taxa. Dimethoate (0.5%) applied as a spot treatment to wet areas of the manure also did not reduce predator abundance. Permethrin (0.05%) applied as a direct treatment to the hens resulted in slight reductions in numbers of Histeridae and Staphylinidae in the manure. A resurgence of Fanniinae occurred at one site 3 wk after permethrin application. Treatment of whole houses with dimethoate (0.5%) resulted in short-term reductions (up to 3 wk) of predatory mites and reductions of Histeridae and Staphylinidae for 4-10 wk.     

Blowflies (Diptera: Calliphoridae) activity in sun exposed and shaded carrion in Portugal

The first forensic entomological study performed in Portugal is presented. Two piglet (Sus scrofa L.) carcasses were used to determine adult Calliphoridae activity on carrion over a period of 121 days, all along the end of spring and the summer, both in a shaded and a sunny site. Five decomposition stages were observed and a total of 10723 adult Calliphoridae, belonging to 11 species, were collected. Calliphora vicina, Calliphora vomitoria, Chrysomya albiceps and Lucilia caesar were the dominant species in this study. Decomposition was faster on the carcass exposed to the sun and the number of Calliphoridae specimens was higher there than in the shaded site. It was found a significant effect of the decomposition stage in the number of specimens attracted to the carcass, as well as a significant effect of the interaction between the decomposition stage and insolation regime. Calliphora and Lucilia species did not show preference for sunny or shaded areas. Important differences in the Calliphoridae community structure were found compared to other regions of the Iberian Peninsula, reinforcing the need of further studies in different environments and regions of this geographical area in order to collect information about the local necrophagous fauna used in forensic practice.     

Phylogeny and evolution of Staphyliniformia and Scarabaeiformia: forest litter as a stepping stone for diversification of nonphytophagous beetles

The beetle series Staphyliniformia exhibits extraordinary taxonomic, ecological and morphological diversity. To gain further insight into staphyliniform relationships and evolution, we reconstructed the phylogeny of Staphyliniformia using DNA sequences from nuclear 28S rDNA and the nuclear protein‐coding gene CAD for 282 species representing all living families and most subfamilies, a representative sample of Scarabaeiformia serving as a near outgroup, and three additional beetles as more distant outgroups. Under both Bayesian inference (BI) and maximum likelihood inference (MLI), the major taxa within Staphyliniformia are each monophyletic: (i) Staphylinoidea, (ii) Hydrophiloidea s.l., and the contained superfamilies (iii) Hydrophiloidea s.s. and (iv) Histeroidea, although Staphylinoidea and Hydrophiloidea s.l. are not strongly supported by MLI bootstrap. Scarabaeiformia is monophyletic under both methods of phylogenetic inference. However, the relative relationships of Staphylinoidea, Hydrophiloidea s.l. and Scarabaeiformia differ between BI and MLI: under BI, Staphyliniformia and Scarabaeiformia were sister groups; under MLI, Hydrophiloidea s.l. and Scarabaeiformia were sister groups and these together were sister to Staphylinoidea. The internal relationships in Scarabaeiformia were similar under both methods of phylogenetic inference, with Cetoniinae, Dynastinae + Rutelinae, Hybosoridae, Passalidae, Scarabaeidae and Scarabaeinae recovered as monophyla. Histeridae comprised two major clades: (1) Abraeinae, Trypanaeine and Trypeticinae; and (2) Chlamydopsinae, Dendrophilinae, Haeteriinae, Histerinae, Onthophilinae, Saprininae and Tribalinae. The relationships among early‐divergent Hydrophiloidea differed between BI and MLI, and overall were unresolved or received only moderate to low nodal support. The staphylinoid families Agyrtidae, Hydraenidae and Ptiliidae were recovered as monophyletic; the latter two were sister taxa, and Staphylinidae + Silphidae was also monophyletic. Silphidae was placed within Staphylinidae in close relation to a subset of Tachyporinae. Pselaphinae and Scydmaeninae were both recovered within Staphylinidae, in accordance with recent analyses of morphological characters, although not always with recently proposed sister taxa. None of the four major groups of Staphylinidae proposed by Lawrence and Newton (1982) was recovered as monophyletic. Certain highly specialized staphyliniform habits and morphologies, such as abdominal defensive glands and reduced elytra, have arisen in parallel in separate lineages. Further, our analyses support two major transitions to an aquatic lifestyle within Staphyliniformia: once within Staphylinoidea (Hydraenidae), and once within Hydrophiloidea s.l. (Hydrophiloidea s.s.). On a smaller scale, the most common transition is from litter to subcortical or to periaquatic microhabitats and the next most common is from litter to carrion and to fungi. Overall, transitions to periaquatic microhabitats were the most numerous. The broad picture in Staphyliniformia seems to be a high level of evolutionary plasticity, with multiple possible pathways to and from many microhabitat associations, and litter as a major source microhabitat for diversification. In Scarabaeiformia, the most common transitions were from litter to foliage, with flowers to litter, litter to flowers, and litter to dung being next, and then litter to roots, logs or carrion. Litter is again the largest overall source microhabitat. The most common transitions were to foliage and flowers. It thus seems that the litter environment presents ecological and evolutionary opportunities/challenges that facilitate entry of Staphyliniformia and Scarabaeiformia into ‘new’ and different ecological adaptive zones.     

Apex predators and the facilitation of resource partitioning among mesopredators

Apex predators may influence carnivore communities through the suppression of competitively dominant mesopredators, however they also provide carrion subsidies that could influence foraging and competition among sympatric mesopredators when small prey is scarce. We assessed coyote Canis latrans and red fox Vulpes vulpes winter diet overlap and composition from scats collected in two study areas with 3‐fold difference in grey wolf Canis lupus density due to a wolf control program. We hypothesized that differences in diet composition would be driven by the use of carrion, and tested whether 1) apex predators facilitate resource overlap, or 2) apex predators facilitate resource partitioning. We estimated the available biomass of snowshoe hares and voles based on pellet density and vole capture rates in each study area. We used molecular analysis to confirm species identification of predator scats, and used microscopic evaluation of prey remains to analyze diet composition of 471 coyote and fox scats. Ungulate carrion, voles and snowshoe hares comprised 73% of coyote and fox diet, and differences in use of carrion and microtines accounted for nearly 60% of the dissimilarity in diet among these canids. Carrion was the top‐ranked item in the coyote diet in both study areas, whereas carrion use by red foxes declined 3‐fold in the study area with higher wolf and small prey abundance. Diet overlap tended to be lower and diet diversity tended to be higher where wolves were more abundant, though these trends were not statistically significant. Taken together, our findings indicate that carrion provisions could facilitate resource partitioning in mesocarnivore communities by alleviating exploitation competition for small mammals.     

Trophic associations of a dung beetle assemblage (Scarabaeidae: Scarabaeinae) in a woodland savanna of Botswana

Species richness and abundance of dung beetles were assessed across a range of bait types that acted as surrogates for the food resources available in Chobe National Park, Botswana. These bait types were comprised of the dung of pig (omnivore), cattle (ruminant herbivore dropping fine-fiberd pads), sheep (pellet-dropping ruminant herbivore), and elephant (monogastric, nonruminant herbivore producing coarse-fibered droppings), and chicken livers (carrion). Species richness was similar between traps baited with pig, cattle, and elephant dung but was relatively lower in those baited with sheep dung and carrion. In traps baited with pig dung, abundance was relatively greater than in all other bait types. A cluster analysis of species abundance distributions for the 30 most abundant species identified four different patterns of bait type association at a 60% level of similarity. All but 1 of the 15 species in cluster A were attracted primarily to the dung of omnivores and pad-dropping ruminant herbivores (pig and cattle). All seven species of cluster B were attracted primarily to coarse-fibered, nonruminant herbivore dung (elephant). All four species of cluster C were primarily carrion and pig dung associated, whereas all four species of cluster D were carrion specialists. In conclusion, the most abundant species were attracted to all bait types, but most species were largely specialized to different dung types or carrion, with dung attracting the majority of the fauna in terms of both species richness and abundance.     

Kairomonal range of generalist predators in specialized habitats: responses to multiple phloeophagous species emitting pheromones vs. host odors

We evaluated responses of the predominant predators of pheromone-producing bark beetles (Coleoptera: Scolytidae) to chemical cues associated with other phloeophagous species that colonize the same trees. This study considered the range of chemical signals exploited by a category of predators that may be viewed either as specialists, because they feed almost exclusively within trees killed by bark beetles, or as generalists, because they feed on a diverse fauna of primary and secondary insects within this habitat. It also evaluated one aspect of a broader model of predator-prey coevolution, that proposes altered semiochemistry as a source of partial escape from predators that exploit kairomones. The predators, Thanasimus dubius (F.) (Coleoptera: Cleridae) and Platysoma cylindrica (Paykull) (Coleoptera: Histeridae), were attracted to cues associated with feeding on bark-phloem disks by two scolytids that produce adult pheromones, Ips pini (Say) and Ips grandicollis (Eichhoff). These predators were not attracted to beetles that feed on lower stems or roots and are not known to produce adult pheromones,Dendroctonus valens LeConte, Hylastes porculus Erickson (Coleoptera: Scolytidae), and Hylobius pales (Herbst) (Coleoptera: Curculionidae). The predator Tenebroides collaris (Sturm) (Coleoptera: Trogositidae) was attracted to I. pini and I. grandicollis, and also to D. valens, H. porculus, and H. pales. Ips pini was attracted to conspecifics only, but I. grandicollis was attracted both to its conspecifics and to volatiles associated with feeding lower stem and root insects. Lower stem and root insects were not or only weakly attracted to cues associated with their conspecifics. These results are consistent with a dynamic coevolved interaction between T. dubius and P. cylindrica and Ips spp.     

Comparative histology of mushroom bodies in carnivorous beetles of the suborder polyphaga (Insecta, Coleoptera)

Mushroom bodies in beetles of the families Histeridae, Staphylinidae, Cantharidae, Trogossitidae, Peltidae, Cleridae, Malachiidae, and Coccinellidae are shown to be rather poorly developed. The calyx region of the mushroom bodies in these beetles never forms two separate cups, and the peduncular apparatus includes a unified shaft almost over its entire length. Only the pedunculus contains two separate shafts in a few cases. Two proliferative centers consisting of one to three neuroblasts are often found in each Kenyon cell group. The shift from carnivorous to feeding on pollen or leaves, which has taken place in some taxa, does not visibly affect the degree of mushroom body development.     

Predator density manipulation and its effects on populations of Rhopalosiphumpadi (Horn.: Aphididae) in spring barley

Experiments were carried out in 1981-83 to assess the impact of polyphagous predators (e.g. Carabidae, Staphylinidae and Araneae) on populations of cereal aphids in spring barley in Sweden. Barriers were erected around mid-field and field-edge plots at different times during the aphids' establishment phase in order to manipulate the predation pressure during the aphid pre-peak period; predators were emigrating from field boundaries. Rhopalosiphum padi was the dominant species of cereal aphid in 1981 and 1982, and was abundant in both years. Reduction of the predation pressure resulted in R. padi populations that were two to six times larger compared with those in unenclosed control plots. Aphid populations were much larger when the predation pressure was reduced earlier in June than when this was done later, in both years, since late erection of barriers excludes fewer predators because most had already entered the enclosed areas. In 1983, R. padi and Sitobion avenae were equally common but occurred in low numbers, and the effects of reducing the predation pressure were less obvious. Bembidion spp. (B. lampros and B. quadrimaculatum) and linyphiid spiders were the most abundant predators during the early establishment phase of aphid populations in each year, and significant inverse correlations were found between peak numbers of R. padi per shoot and numbers of predators from these taxa in 1981 and 1982. Similar relationships were found between total aphids and numbers of Staphylinidae, B. quadrimaculatum and Coccinella septempunctata in 1983. It was concluded that differences between the manipulated numbers of polyphagous predators caused the observed differences in peak population levels of R.padiin 1981,1982 and to a lesser extent, 1983. Apparent levels of parasitism and fungal disease were low during the pre-peak period. Aphid specific predators, abundant after the peak, were considered partly responsible for the decline of aphid populations each year. The results are compared with those from similar experiments elsewhere with S. avenae and Metopolophium dirhodum in winter wheat. Reasons why the effects of polyphagous predators are greater, and occur over a much shorter period of time in Sweden are discussed.     

Oviposition preferences and antennal size in carrion flies

Carrion-feeding flies use odours emanating from the decomposing corpse as cues for oviposition and are described as generalists because the larvae feed on the corpses of diverse species. Whereas several features of the corpse may influence the oviposition choices of these flies, it is not known whether there is a preference for a particular species of corpse. We provided carrion flies with ovipositional (and feeding) choices in a field experiment, in which various odour sources were presented simultaneously. We found novel evidence of broadly consistent choices of carrion by flies from four families. Traps baited with decaying fish flesh captured the greatest number of individuals, whereas traps baited with decaying pig liver typically attracted the least. We also asked whether individuals captured in the various baits vary in antennal size, perhaps reflecting different capacities for odour detection. There was a trend for individuals of Lucilia sericata Meigen (Diptera: Calliphoridae) and the platystomatid collected from the traps baited with pig liver to have significantly larger antennae, whereas individuals of Muscina stabulans (Fallen) (Diptera: Muscidae) captured in traps baited with marine fish flesh had relatively longer antennae for their body size. Our data reveal a more nuanced pattern of oviposition behaviour in these generalist carrion flies, which may reflect differences in their preference of carrion with different nutrients, and in their capacity to detect particular odours.