Hoverfly (Diptera: Syrphidae) community of a cultivated arable field and the adjacent hedgerow near Debrecen,Hungary

A hoverfly (Syrphidae) community was investigated in a cultivated wheat field and the adjacent hedgerow near Debrecen (Hungary). We monitored the change of species richness and abundance of hoverflies along three transects in the hedgerow and in the wheat field in different distances (10 m, 20 m) from the hedgerow. The effect of sampling methods on the number of hoverfly species and individuals was analyzed. Two sampling methods were used to catch hoverflies: netting and pan traps. The whole sampling period was divided into three subperiods, which are early (22^nd April–2^nd June), middle (11^th June–1^st August) and late (6^th August–11^th September). Altogether 1,214 individuals of 22 species were sampled. Fourteen species with 78% of individuals belonged to the aphidophagous group, feeding on aphids as larvae. Altogether 861 individuals of 22 hoverfly species were sampled by netting and 353 individuals of 10 species by pan traps. The total number of hoverfly species was significant lower in the late period than in the early. The total abundance was higher in the middle period compared to the early. The species richness and abundance of aphidophagous species followed a similar pattern as the total species values. The species richness and abundance of hoverflies were significant higher in 10 m and 20 m distance in the wheat field than along the hedgerow. The results suggest that the pan traps were less efficient in the hedgerow than the netting, but in the wheat field they sampled more hoverflies because of visually alluring effect on hoverflies in the absence of flowers.     

Hoverflies (Diptera,Syrphidae) in Agrolandscapes of St. Petersburg and Leningrad Province

A total of 57 species from 32 genera of hoverflies (Diptera, Syrphidae) were found in the agricultural landscapes of St. Petersburg and Leningrad Province. One species, Cheilosia vulpina (Mg.), was recorded in the region for the first time. The largest numbers of species occurred at forest and field edges covered with wild grasses and shrubs, while 21 species of hoverflies were recorded in crops. The species most commonly found in crops were representatives of the genera Melanostoma, Sphaerophoria, and Platycheirus whose larvae feed on aphids.     

Contrasting resource-dependent responses of hoverfly richness and density to landscape structure

Hoverflies (Diptera: Syrphidae) in agroecosystems have gained much attention recently because the larvae of some species are efficient control agents of crop aphids, and adult hoverflies provide pollination services to wild flowers and flowering crops. We assessed the density and species richness of hoverflies in 32 calcareous grasslands, which constitute a semi-natural habitat for adult hoverflies, by means of six transect walks from April to September 2004. Our results show that local habitat factors and landscape factors influenced hoverfly communities, and that their effects on hoverfly richness and density were quite contrary. Hoverfly species richness was affected by factors related to resource heterogeneity such as species richness of flowering plants, area of grassland habitat, and landscape diversity, which all imply the availability of diverse micro- and macrohabitats for adults and larvae. Hoverfly density, in contrast, depended on factors related to resource quantity, such as the amount of pollen and nectar resources for adults and the amount of larval macrohabitats in the surrounding matrix. Therefore, both adult and larval habitat requirements have to be considered when analysing hoverfly communities in agricultural landscapes. Species guilds responded to specific land-use types such as annual crops and woodland at different spatial scales, indicating variation in species’ mobility and in the degree of spillover effects among neighbouring landscape elements.     

Indiscriminate oophagy by ant larvae: an explanation for brood serial organization?

Summary Last instar larvae ofLasius niger under standard laboratory conditions and abundant food supply feed on conspecific eggs and, if forced to a choice, show a significant statistical preference for trophic versus fertilized eggs (approx. 60% of the trials observed). On the other hand, they are unable to discriminate between kin and non-kin eggs, both fertilized and trophic. Fertilized eggs killed by freezing and trophic eggs handled in the same way are also selected in a random manner.Last instar larvae ofMessor semirufus regularly failed to discriminate in a significant way between trophic and fertilized and between kin and non-kin eggs.Substantial experimental evidence confirms that larvae of both these species — as already suggested in the literature for other ants-rely on trophic eggs as an essential component of their diet in order to be able to develop. Additionally,L. niger last instar larvae appear to be able to attack and pierce the egg chorion with their own mandibles, while this capacity is at least very reduced or very rare inM. semirufus. First and second instar larvae of both species never succeeded in piercing the egg membrane alone.These findings imply that the right (i.e. trophic) eggs should be presented to the larvae by the workers (i.e. worker discrimination should be assumed) and, at least in the case of youngLasius larvae, and probably for all stages ofMessor larvae, the egg membrane must be pierced by the workers in order to allow the larvae to feed.The following evolutionary sequence is suggested to explain the origin of trophic eggs in ants: 1) larval oophagy (obligatory at least for the species founding new colonies in an independent claustral manner), 2) generalized facultative or obligatory larval oophagy for larvae of all colonial stages, 3) production of trophic eggs by the queen(s) and/or workers in order to avoid cannibalism of nestmates.Lack of discrimination or weak discrimination capacity between trophic and fertilized eggs and the consequent larval cannibalism in form of oophagy, as demonstrated in this paper, is suggested to explain age segregation among eggs and larvae from workers, a widespread phenomenon in ants which must have been selected to avoid the oophagy of viable eggs.     

An exceptionally high diversity of hoverflies (Syrphidae) in the food of the reed warbler (Acrocephalus scirpaceus)

Despite being considered a classical example of protective Batesian mimicry hoverflies (Syrphidae) are known to be preyed upon by various passerines. The aim of the present study was to examine in detail food brought by reed warblers Acrocephalus scirpaceus to their nests to better understand the importance of hoverflies in the diet of small passerines. Using neck collars, 273 food samples containing 8,545 food items delivered to reed warbler and parasitic common cuckoo Cuculus canorus nestlings in warbler nests were recorded. The study was conducted during three breeding seasons in South Moravia, Czech Republic. An unusually high diversity of hoverflies was found — 27 species, including Mesembrius peregrinus (critically endangered species in the Czech Republic) and Mallota cimbiciformis (endangered species) — a new taxon to the Czech Republic. This indicates that nestling diet analyses may provide not only information on avian foraging behaviour but also important faunistic data. Thus, without the detailed identification to species level of material from foraging behaviour studies valuable scientific information may be lost. Overall dominance of Syrphidae was 3.7%, the most common species being Episyrphus balteatus (55.7%, n = 318). However, this number seriously underestimates the importance of hoverflies in the diet of reed warblers as hoverflies are one of the largest prey taken by warblers. Both larvae and pupae were rare, imagines strongly dominating (92.7%). Both specific wasp mimics (e.g., Chrysotoxum verrali) and bee mimics (e.g., Eristalis spp.) were not avoided by foraging reed warblers. The presence of a parasitic cuckoo chick did not affect host foraging behaviour with respect to overall dominance of hoverflies in the diet (warbler 3.3%, cuckoo 3.8%).     

Diversity and phenology of hoverflies (Diptera: Syrphidae) in pine forests (Pinus halepensis Miller) of Algeria

Hoverflies are good indicators of ecosystem integrity, especially in drylands. However, the key factors explaining hoverfly diversity in North African forest ecosystems are still not addressed. The current study provides data on the diversity, structure and functional trophic groups (FTG) of the hoverfly community in Aleppo pine forests under a semi-arid climate in northeastern Algeria. Using an entomological net, hoverflies were sampled weekly during 2008–2009. Alpha and beta-diversity of hoverflies and functional trophic group (FTG) were analyzed using several parameters and indices (e.g. species composition, richness, occurrence, diversity, estimations, similarity, etc.). In total, 602 individuals of 21 species were collected with a constant species (Eupeodes corollae) and four common species (Episyrphus balteatus, Chrysotoxum intermedium, Eristalis arbustorum and Eristalis tenax). Most species (17) occurred accidentally or very accidentally in samples. The highest diversity was recorded during spring, corresponding to the flowering season of most understory plant species. Seasonal rarefaction and extrapolation curves indicated that the expected species richness would be higher in autumn and spring compared to summer and winter. The spectrum of FTG ranked predators first with 52.4% of species, followed by saprophagous (42.8%) and then phytophagous (4.8%) species. Hoverfly communities showed high taxonomic richness and alpha-diversity all over the year, with peaks during spring that coincides with flowering period of most plant species of the forest understorey and favourable climatic conditions.     

Species diversity of Ichneurnonidae and Serphidae (Hymenoptera) in an English suburban garden

In the two-year period, 1972–73, 6445 Ichneumonidae of 455 species were caught in a Malaise trap operated in a suburban garden in Leicester, England. An additional 74 species were trapped in 1974. The collection includes a number of species new to the British list. The flight season of ichneumonids extended from March to November or December, with peak abundance and diversity in August. Size of trap samples fluctuated erratically, depending on air temperature. No species was particularly common and many were rare, 141 being taken once only in the two-year period. The commoner species were present throughout the season, supporting the suggestion that ichneumonids are niche-specific rather than host-specific. Parasites of aphidophagous Neuroptera and Syrphidae, of spiders, of micro-Lepidoptera, and of Diptera found in decaying plant material were especially abundant, as is characteristic of the British fauna as a whole. Adult ichneumonids are mobile, and it is assumed that the Malaise trap was sampling an area far larger than the garden in which it was sited, although suburban gardens are a particularly favourable habitat for ichneumonids. Twenty-two species of Serphidae were captured in the Malaise trap during 1972–74, five of them new to Britain.     

The role of odour and visual cues in the pan-trap catching of hoverflies (Diptera: Syrphidae)

Coloured pan traps are frequently used to attract and catch insects, such as in the monitoring of populations of beneficial insects in classical or conservation biological control. They are also used in the evaluation of the recovery of insect populations after disturbance and in many other situations where an estimate of relative insect numbers is required. However, the fact that traps may be visible to the insects over a considerable distance can influence the interpretation of catch data. This difficulty may arise, for example, if traps along a transect can attract insects from some or all of the other transect positions. This study compared the effect of different coloured traps on attraction and catch of hoverflies. The hypothesis was that completely yellow traps would attract hoverflies from a distance, while traps that were green outside and yellow inside would catch fewer flies because only those from above or near the trap can see the yellow stimulus. A subsidiary hypothesis was that rose water would enhance hoverfly capture rates. For the two main hoverfly species captured, Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart), significantly more individuals were caught in completely yellow traps than in yellow and green or in completely green traps. Moreover, the addition of rose water increased the number of hoverflies caught significantly. It is suggested that if a measure of hoverfly numbers relating to a particular distance along a transect is required, consideration should be given to the ability of hoverflies to see yellow traps from a distance. The use of traps that are green outside would more accurately reflect the local abundance of hoverflies. If higher trap catches of hoverflies are needed for statistical purposes, rose water can enhance catches.     

Indirect plant-mediated interactions among parasitoid larvae

Communities are riddled with indirect species interactions and these interactions can be modified by organisms that are parasitic or symbiotic with one of the indirectly interacting species. By inducing plant responses, herbivores are well known to alter the plant quality for subsequent feeders. The reduced performance of herbivores on induced plants cascades into effects on the performance of higher trophic level organisms such as parasitoids that develop inside herbivores. Parasitoids themselves may also, indirectly, interact with the host plant by affecting the behaviour and physiology of their herbivorous host. Here, we show that, through their herbivorous host, larvae of two parasitoid species differentially affect plant phenotypes leading to asymmetric interactions among parasitoid larvae developing in different hosts that feed on the same plant. Our results show that temporally separated parasitoid larvae are involved in indirect plant-mediated interactions by a network of trophic and non-trophic relationships.     

Effects of climate change on the distribution of hoverfly species (Diptera: Syrphidae) in Southeast Europe

Climate change presents a serious threat to global biodiversity. Loss of pollinators in particular has major implications, with extirpation of these species potentially leading to severe losses in agriculture and, thus, economic losses. In this study, we forecast the effects of climate change on the distribution of hoverflies in Southeast Europe using species distribution modelling and climate change scenarios for two time-periods. For 2041–2060, 19 analysed species were predicted to increase their areas of occupancy, with the other 25 losing some of their ranges. For 2061–2080, 55% of species were predicted to increase their area of occupancy, while 45% were predicted to experience range decline. In general, range size changes for most species were below 20%, indicating a relatively high resilience of hoverflies to climate change when only environmental variables are considered. Additionally, range-restricted species are not predicted to lose more area proportionally to widespread species. Based on our results, two distributional trends can be established: the predicted gain of species in alpine regions, and future loss of species from lowland areas. Considering that the loss of pollinators from present lowland agricultural areas is predicted and that habitat degradation presents a threat to possible range expansion of hoverflies in the future, developing conservation management strategy for the preservation of these species is crucial. This study represents an important step towards the assessment of the effects of climate changes on hoverflies and can be a valuable asset in creating future conservation plan, thus helping in mitigating potential consequences.     

西藏朗错秋季裸鲤属营养生态位及种间食物关系

西藏朗错海拔4300 m,是典型的高原湖泊之一。湖内具有兰格湖裸鲤和拉孜裸鲤共存的现象。本研究采用碳、氮稳定同位素技术分析了2018年秋季兰格湖裸鲤和拉孜裸鲤的食物组成和营养生态位,探讨了两种裸鲤的种间食物关系,包括饵料相似性和重叠系数。结果表明: 兰格湖裸鲤主要摄食蜉蝣类幼虫、摇蚊类幼虫、着生藻类、钩虾类和浮游生物;拉孜裸鲤主要摄食蜉蝣类幼虫、着生藻类、摇蚊类幼虫、钩虾类和水生维管束植物。两种裸鲤的营养生态位存在重叠,兰格湖裸鲤的δ¹³C值变幅(CR=1.60)、δ¹⁵N值变幅(NR=1.89)和凸多边形,总面积(TA=1.80)均小于拉孜裸鲤,差值分别为0.09、0.57和1.29。两种裸鲤的饵料相似性系数(94.2％)和重叠系数(91.5%)均较高,表明秋季西藏朗错两种裸鲤可能存在激烈的种间食物竞争关系。     

Variability in the trophic position of larval fish in a coastal pelagic ecosystem based on stable isotope analysis

We used stable isotopes of carbon (C) and nitrogen (N) to investigatethe trophic position of six species of larval fish in the pelagicecosystem of coastal Newfoundland. Isotope profiles from phytoplankton,net plankton and macrozooplankton were consistent with previousstudies. All species of larval fish showed a length-dependentshift in ¹³C that indicates a move to a pelagic diet from thecombined pelagic and demersal eating habits of the adult spawners.The trophic position of four larval fish species (American plaice,yellowtail flounder, cunner, radiated shanny) was consistentwith them feeding primarily on copepods, as expected from stomachcontent analysis. The ¹⁵N-based trophic position of larval witchflounder and capelin indicates that they feed significantlyon phytoplankton and heterotrophic protists from the microbialloop, respectively; this evidence contrasts with stomach contentanalysis. Although links between larval fish and the microbialloop are not considered as common as is the link with crustaceanzooplankton, this and other studies challenge the long-heldbelief that marine fish larvae feed effectively exclusivelyon copepods.     

Effect of hunger on yellow water trap catches of hoverfly (Diptera: Syrphidae) adults

1 An experiment was conducted in a winter wheat field using yellow water traps at crop height and at ground level, near to and distant from flowers, to test the hypothesis that such traps are seen as a source of food by flower‐feeding adult hoverflies and are therefore likely to selectively trap hungry individuals. Hoverflies caught in each trap were counted and identified and the amount of pollen in their guts was assessed. Ratios of numbers of hoverflies seen in the wheat crop to numbers caught in nearby traps were compared for the different treatments. 2 Most hoverflies were caught in crop‐high traps but they included a high proportion of individuals with empty guts. The taxa were: Episyrphus balteatus (De Geer), Metasyrphus corollae (F.) (these species together accounted for over 90% of the individuals trapped), with Sphaerophoria spp., Syrphus spp., Scaeva pyrastri (L.), Melanostomini and unidentified others making up the rest. 3 Significantly fewer hoverflies were captured in low than in high traps. The ratios of numbers trapped to numbers observed, in flower and in no flower treatments would be expected to be the same if the traps were not selective. This was supported for low traps. With high traps, however, there was a highly significant difference between the ratios (71.34 and 126 : 8, respectively). 4 Flies captured in high traps had less pollen in their gut than those captured in low ones. At each distance, more E. balteatus captured in high traps were in pollen category 1 (< 20 grains) than in any other category. The opposite state was seen in low trap catches, where most flies were in category 5 (> 5000 grains). Median pollen categories were 2 (21–200 grains) and 4 (1501–5000 grains) for flies caught in high and low traps, respectively. 5 The ecological selectivity of traps according to their height and the physiological condition of the targeted individuals is a problem likely to affect many trapping systems apart from the one described in this paper.     

Urban domestic gardens (VIII) : environmental correlates of invertebrate abundance

Domestic gardens associated with residential zones form a major component of vegetated land in towns and cities. Such gardens may play a vital role in maintaining biodiversity in urban areas, but variation in the abundance of organisms in gardens has been little explored. We report the results from a case study of 61 domestic gardens in the city of Sheffield, UK. Across 22 invertebrate groups, the median number of individuals recorded per garden was 49, 178, and 1012 in litter collections, pitfall and Malaise trap samples, respectively. Abundance was analysed by stepwise multiple regression and hierarchical tree analysis in relation to garden and landscape variables. The amount of variation explained in regression models ranged from 4 to 56%, for data based on pitfall and litter samples, and from 16 to 92% for data from Malaise traps. In total, 31 out of 36 explanatory variables entered into stepwise regression models, and 29 of them did so more than once. Although there was strong evidence only for approximately half of such relationships, in these cases the two methods of analysis corroborated one another. General correlates of invertebrate abundance were lacking, and likely reasons for inconsistencies in the relationships are discussed in the context of sampling and species biology. Correlates of the greatest significance occurred at both landscape (e.g. altitude) and garden scales (e.g. area of canopy vegetation). These factors were associated with species richness as well as abundance.     

Urban domestic gardens (VI): environmental correlates of invertebrate species richness

Domestic gardens associated with residential zones form a major component of undeveloped land in towns and cities. Such gardens may play a vital role in maintaining biodiversity in urban areas, but explanations for the variation in the richness of species assemblages in gardens are lacking. We report the results from a case study of 12 invertebrate groups in 61 domestic gardens in the city of Sheffield, UK. The mean number of species within a taxon, recorded per garden, was no greater than 3, 10, and 20 species in litter, pitfall trap and Malaise trap samples, respectively. Relatively speciose groups exhibited high turnover between gardens, with typically 50% of the group occurring only once. In contrast, several species-poor taxa were virtually ubiquitous. Species richness was analysed by multiple regression and hierarchical tree analysis in relation to garden and landscape variables. In general, the two methods of analysis corroborated one another. In total, 22 explanatory variables entered into regression models, although 12 of them only did so once. The amount of variation in species richness explained in models was generally quite high, with the factors involved operating over a range of scales. However, the patterns that emerged were not consistent across taxa. The most important predictors of species richness, of relevance to land use planners, were components of garden vegetation, especially the abundance of trees. Likely reasons for inconsistencies in the relationships are discussed in the context of sampling and species biology.     

Four species of mosquito as possible vectors for Dirofilaria immitis piedmont rice-fields

Wild mosquitoes were allowed to feed, during two nights, on a heartworm-infected dog with a very high microfilaraemia (72,000 and 78,000 microfilariae/ml just prior to be allocated in the live trap). A heartworm-free dog was used as control bait in the second night. Engorged mosquitoes (Aedes caspius, Anopheles maculipennis s.l., Culex modestus, and Cx pipiens) were kept under laboratory conditions, artificially fed until day 10 post-infection (PI) and then dissected for the presence of Dirofilaria immitis larvae. Mortality of Ae. caspius and Cx modestus was significantly higher than controls on day 3 PI (89.4 and 80.3%, respectively), but survival rates were similar in the following period. Third-stage larvae were observed from day 12 to 17 PI in the four mosquito species studied. However, vector efficiency was significantly higher in Ae. caspius which produced 102 (73.9%) of the 138 infective larvae found. Although less efficient vectors, the other 3 species may contribute to D. immitis transmission in the study area due to their abundance (Cx modestus) or higher resistance to the negative effects of infection (An. maculipennis s.l., Cx pipiens). As far as Cx pipiens is concerned, this mosquito, which luckily fed the least frequently on the dog, confirmed to act as powerful vector in iperendemic areas. The risks for veterinary and medical health, related to the zoo-antropophylic host-feeding pattern of the studied species, are discussed.     

Hoverfly (Diptera, Syrphidae) fauna of Ary-Mas locality (the Taimyr Biosphere Reserve)

The local fauna of Ary-Mas (the Taimyr Biosphere Reserve) was found to comprise 56 species of hoverflies, representing only two subfamilies: Syrphinae (36 species) and Eristalinae (20 species). Analysis of trophic preferences of adult hover-flies showed that Syrphidae visited plants of 17 species from 10 families. The representatives of Syrphidae preferred Tanacetum bipinnatum (18 species), Ranunculus propinquus, and Tripleurospermum hookeri (12 species each). Three species of hoverflies visited the greatest number of plant species: Melangyna arctica (11), Syrphus ribesii (9), and Parasyrphus dryadis (8).     

Hoverflies (Diptera: Syrphidae) benefit from a cultivation of the bioenergy crop Silphium perfoliatum L. (Asteraceae) depending on larval feeding type,landscape composition and crop management

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Revealing species-specific trophic links in soil food webs: molecular identification of scarab predators

Soil food webs are particularly important in terrestrial systems, but studying them is difficult. Here we report on the first study to apply a molecular approach to identify species-specific trophic interactions in below-ground food webs. To identify the invertebrate predator guild of the garden chafer Phyllopertha horticola (Coleoptera, Scarabaeidae) whose root-feeding larvae can be highly abundant in grasslands, a specific DNA marker was developed. It allowed detection of P. horticola egg and white grub meals within the gut content of Poecilus versicolor (Coleoptera, Carabidae) larvae for up to 24 h post-feeding. Soil samples from an alpine grassland revealed a diverse below-ground macro-invertebrate community with earthworms, P. horticola larvae, and centipedes as well as beetle larvae as the most abundant detritivores, herbivores, and predators, respectively. Garden chafer DNA was detected in 18.6%, 4.1%, and 4.4% of field-collected Geophilidae (n = 124), beetle larvae (n = 159), and Lithobiidae (n = 49), respectively. We conclude that most of the investigated predators actively preyed on P. horticola, as secondary predation is unlikely to be detected in below-ground systems. Moreover, scavenging most likely contributes only to a small percentage of the revealed trophic links due to the low availability of carrion. Sampling date did not influence prey detection rates, indicating that both P. horticola eggs and larvae were preyed on. Only 2.7% of the below-ground predators tested positive for earthworms, an alternative, highly abundant prey, suggesting that P. horticola represents an important prey source for centipedes and predatory beetle larvae during summer within the soil food web.