Larvae of the exotic predatory ladybird <Emphasis Type="Italic">Platynaspidius maculosus</Emphasis> (Coleoptera: Coccinellidae) on citrus trees: prey aphid species and behavioral interactions with aphid-attending ants in Japan

An aphidophagous ladybird, Platynaspidius maculosus (Weise) (Coleoptera: Coccinellidae), is originally distributed in China, Taiwan, and Vietnam. The ladybird has recently intruded into the southern and central parts of Japan. The present study found that the larvae of this ladybird preyed on three aphid species, Aphis spiraecola, Aphis gossypii, and Toxoptera citricidus (all Hemiptera: Aphididae), feeding on young shoots of various Citrus species in August to early October in Shizuoka Prefecture, central Japan. Laboratory rearing of the sampled larvae confirmed that the larvae completed their development (adult emergence) by consuming each of the three aphid species. The ladybird larvae were observed foraging in aphid colonies attended by one of the four ants, Lasius japonicus, Pristomyrmex punctatus, Formica japonica, and Camponotus japonicus (all Hymenoptera: Formicidae). Field observations revealed that the foraging/feeding larvae were almost completely ignored by honeydew-collecting ants even when they physically contacted each other. Thus, in Japan, the larvae of the exotic ladybird exploit colonies of the three aphid species attended by one of the four ant species on many Citrus species. On the basis of the results, I discuss the possibility of the ladybird’s reproduction on citrus trees in Japan, probable adaptations of the ladybird larvae to aphid-attending ants, and potential impacts of the ladybird on native insect enemies attacking ant-attended aphids on citrus.     

Long term changes in the communities of native ladybirds in Northern Italy: impact of the invasive species <Emphasis Type="Italic">Harmonia axyridis</Emphasis> (Pallas)

Since the mid-2000s, the exotic coccinellid species Harmonia axyridis (Pallas) has established itself in Northern Italy, raising serious concerns about possible repercussions on native ladybirds. In this study we compared the ladybird assemblages in 2015–2016 with those sampled in 1995–1996, before the arrival of H. axyridis. Surveys were carried out in the same sites and with the same methods for both periods. Aphidophagous ladybirds were sampled in hedgerows and herbaceous habitats at field margins by mechanical knockdown and sweeping net, respectively. The changes in the structure of ladybird communities after the arrival of H. axyridis were significantly different between arboreal and herbaceous habitats. Harmonia axyridis is currently the dominant species in shrubs and trees, and all the native ladybird species taken together account for only approximately one third of the total individuals sampled in 2015–2016. On the other hand, the relative abundance of the exotic species in herbaceous habitats was low, and it has had a negligible relevance on the structure of ladybird communities on grasslands. Among native species, Adalia bipunctata (L.), whose ecological niche largely overlaps with that of H. axyridis, suffered the largest decline between 1995–1996 and 2015–2016. The co-occurrence of H. axyridis invasion and the regression of A. bipunctata suggest a direct impact of the exotic species, because no other major modifications occurred in the studied areas between sampling periods.     

Species assemblages of ladybirds including the harlequin ladybird <Emphasis Type="Italic">Harmonia axyridis</Emphasis>: a comparison at large spatial scale in urban habitats

We evaluated the status of native ladybird assemblages in the presence of the non-native ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in three European countries. To achieve this, we assessed the abundance of ladybirds from common host plants in urban areas of Great Britain, Czech Republic and Slovak Republic in 2014. We determined (i) the effects of season, host plant, location, abundance of H. axyridis and aphids on the ladybird species assemblage, (ii) the relationship between ladybird abundance and aphid density, (iii) the relationship between diversity of native ladybird species and the abundance of H. axyridis. There was a non-linear relationship between abundance of ladybirds and abundance of aphids but we found the abundance of other ladybird species was not correlated with H. axyridis. We highlight the value of large-spatial scale studies for revealing patterns in community assemblages and ultimately informing understanding of ecosystem resilience.     

<Emphasis Type="Italic">Lecanicillium muscarium</Emphasis> and <Emphasis Type="Italic">Adalia bipunctata</Emphasis> combination for the control of black bean aphid<Emphasis Type="Italic">, Aphis fabae</Emphasis>

The predator Adalia bipunctata (Coleoptera: Coccinellidae) and the entomopathogenic fungus Lecanicillium muscarium, have been considered as potential biological control against aphids. While it can be difficult to achieve a high control level of Aphis fabae Scopoli (Hemiptera: Aphididae) using only a single beneficial agent, the research presented here aimed to determine the interaction between L. muscarium and A. bipunctata potential for control against A. fabae. Lecanicillium muscarium was found to cause about 30% mortality in A. bipunctata and with a reduction in feeding by about 15%. However, co-application of A. bipunctata and L. muscarium can cause an addititive effect in reducing aphid populations, resulting in about 90% reduction in aphid populations compared with control treatment. Thus, these two biocontrol agents have the potential to be complementary. This research study demonstrates that it is possible to combine A. bipunctata with L. muscarium to provide a sustainable method for management of A. fabae on broad bean cropping system and that field studies are required.     

Functional convergence and phenotypic divergence in two specialist species of pine-associated ladybirds

Traditionally, convergent evolution has been considered to produce phenotypic similarity in independently evolved species. By contrast, recent studies have detected morphological divergence between species even in similar selective environments when different morphological traits combine to produce a specific functional output. However, it is still unclear whether a complex combination of non-morphological phenotypic traits, such as behavioural and life-history traits, can produce a similar performance in different species. In this study, I examined prey capture performance and related phenotypes in two sympatric ladybird species, Sospita oblongoguttata and Harmonia yedoensis, which specialize on the giant pine aphid, which is known to be elusive for ladybird hatchlings. In particular, I focused on egg size and proportion of trophic eggs in the clutch, since the amount of maternal investment per offspring can contribute to prey capture performance of ladybird hatchlings. Predation success of hatchlings against the giant pine aphid was higher in both S. oblongoguttata and H. yedoensis than in Harmonia axyridis, a generalist ladybird species that feeds on various kinds of aphid species in nature. Sospita oblongoguttata females, however, produced relatively larger eggs and in most clutches provided no trophic eggs, whereas H. yedoensis females produced smaller eggs and provided more trophic eggs per clutch. Moreover, hatchling morphology in H. yedoensis more closely resembled that of its congener, H. axyridis, than that of the more distantly related S. oblongoguttata, although like H. yedoensis, S. oblongoguttata predates on the elusive pine aphid. These results in two pine-associated specialist ladybirds indicate that divergent phenotypes can nonetheless have similar prey capture performance. In conclusion, this work demonstrates that the general ultimate function can be achieved by various mechanisms through convergence that operates at different level of life.     

Are aphid parasitoids from mild winter climates losing their winter diapause?

Temperature is both a selective pressure and a modulator of the diapause expression in insects from temperate regions. Thus, with climate warming, an alteration of the response to seasonal changes is expected, either through genetic adaptations to novel climatic conditions or phenotypic plasticity. Since the 1980s in western France, the winter guild of aphid parasitoids (Hymenoptera: Braconidae) in cereal fields has been made up of two species: Aphidius rhopalosiphi and Aphidius matricariae. The recent activity of two other species, Aphidius avenae and Aphidius ervi, during the winter months suggests that a modification of aphid parasitoid overwintering strategies has taken place within the guild. In this study, we first performed a field survey in the winter of 2014/15 to assess levels of parasitoid diapause incidence in agrosystems. Then, we compared the capacity of the four parasitoid species to enter winter diapause under nine different photoperiods and temperature conditions in the laboratory. As predicted, historically winter-active species (A. rhopalosiphi and A. matricariae) never entered diapause, whereas the species more recently active during winter (A. avenae and A. ervi) did enter diapause but at a low proportion (maximum of 13.4 and 11.2%, respectively). These results suggest rapid shifts over the last three decades in the overwintering strategies of aphid parasitoids in Western France, probably due to climate warming. This implies that diapause can be replaced by active adult overwintering, with potential consequences for species interactions, insect community composition, ecosystem functioning, and natural pest control.     

A functional response evaluation of pre-infestation with <Emphasis Type="Italic">Bemisia tabaci</Emphasis> cryptic species MEAM1 on predation by <Emphasis Type="Italic">Propylea japonica</Emphasis> of <Emphasis Type="Italic">Myzus persicae</Emphasis> on host plant tomatoes

Herbivore feeding on host plants may induce defense responses of the plant which influence other herbivores and interacting species in the vicinity, such as natural enemies. The present work evaluated the impact of pre-infestation with the tobacco whitefly Bemisia tabaci cryptic species MEAM 1, on the predation ability of the ladybird Propylea japonica, to the green peach aphid Myzus persicae, on tomato plants. The results show that B. tabaci pre-infestation density, duration, and leaf position, can impact prey consumed by P. japonica under various aphid densities. The aphids consumed by P. japonica in each treatment were fit using the Holling type II functional response equation. The predatory efficiency (a/T _h) of P. japonica was the highest in the treatment with 60 aphids and 48-h infestation directly on damaged leaves. The predatory efficiencies of P. japonica decreased with a reduction of pre-infestation density and duration. We also observed that pre-infestation on young and undamaged leaves increased predation by P. japonica.     

Effect of vegetation cover on the abundance and diversity of ladybirds (Coccinellidae) assemblages in a peat bog

Predaceous ladybirds are important natural enemies of many insect pests in terrestrial ecosystems such as peatlands, which are habitats for specialized cold-adapted plants. Ladybird assemblages of pristine peat bogs have not yet been assessed. In total, 15 ladybird species were recorded in peat bog in Belarus by using entomological sweep net. The present study shows low diversity, evenness and species richness of ladybird assemblages. However, a small number of species were present in high numbers. These are Coccinella hieroglyphica, Chilocorus bipustulatus, Coccinulla qutuordecimpustulata and Hippodamia tredecimpunctata. Ladybird abundance was positively related to shrub cover and number of vascular plant species, and negatively related to herb cover. In terms of ladybird diversity, only shrub cover had a significant negative effect.     

Diversity of the Most Commonly Reported Facultative Symbionts in Two Closely-Related Aphids with Different Host Ranges

Richness and abundance of facultative symbionts vary strongly with aphid species and genotype, symbiont strain, host plant, biogeography, and a number of abiotic factors. Despite indications that aphids in the same ecological niche show similar levels of facultative symbiont richness, existing reports do not consider the potential role of host plants on aphid microbial community. Little is known about how oligophagy and polyphagy may be influenced by secondary symbiont distribution, mainly because studies on secondary symbiont diversity are biased towards polyphagous aphids from the Northern Hemisphere. Here, we demonstrate the richness and abundance of the most common aphid-associated facultative symbionts in two tropical aphid species, the oligophagous Aphis (Toxoptera) citricidus (Kirkaldy) (Hemiptera: Aphididae) and the polyphagous Aphis aurantii (Boyer de Fonscolombe) (Hemiptera: Aphididae). Aphis citricidus is restricted to Citrus sp. host plants and closely related genera, whereas A. aurantii successfully exploits a wide variety of host plants from different families. Both were collected in the same ecological niche and our data basically indicated the same richness of secondary symbionts, but the abundance at which secondary symbionts occurred was very distinct between the two species. Spiroplasma was the most abundant facultative symbiont associated with A. citricidus and A. aurantii in the ecological niche studied. Single and multiple secondary symbiont infections were observed, but diversity of multiple infections was particularly high in A. citricidus. We discuss our findings and suggest hypotheses to explain causes and consequences of the differences in secondary symbiont diversity observed between these two aphid species.     

Intraguild predation on the aphid parasitoid <Emphasis Type="Italic">Aphelinus asychis</Emphasis> by the ladybird <Emphasis Type="Italic">Harmonia axyridis</Emphasis>

We investigated intraguild predation (IGP) on an aphid parasitoid, Aphelinus asychis Walker (Hymenoptera: Aphelinidae), by the multicolored Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), and used the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) as the prey/host in the laboratory. The ladybirds reared on artificial diet and on aphids consumed more aphids than mummies, while those reared on parasitized aphids consumed similar numbers of aphids and mummies. The ladybirds chose more mummies in treatments when mummies were more abundant, and more aphids when numbers of aphids and mummies were equal, or when aphids were more abundant. However, at all density treatments, rejection rates of mummies (36%) were much greater than of aphids (2%). H. axyridis prey on more aphids than A. asychis mummies, which enhances biological control by the two species. However, prior feeding experience affected subsequent choice, increasing the competition between natural enemies which would reduce their combined effectiveness for biological control.     

Potential for exploitative competition,not intraguild predation,between invasive harlequin ladybirds and flowerbugs in urban parks

In aphidophagous insect communities invaded by the harlequin ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae), intraguild predation (IGP) is widely implicated in the displacement of native predators, however, indirect trophic interactions are rarely assessed. Using molecular gut-content analysis, we investigated the relative frequencies of IGP by H. axyridis on the predatory flowerbug Anthocoris nemoralis Fabricius (Heteroptera: Anthocoridae) and prey overlap for a shared prey, the lime aphid Eucallipterus tiliae L. (Hemiptera: Aphididae), in Tilia × europaea crowns in urban parks. The frequency of IGP by H. axyridis was low: 2.7 % of larvae and 3.4 % of adults tested positive for A. nemoralis DNA. The presence of lime aphid DNA in predators was higher: 56.5 and 47.9 % of H. axyridis larvae and adults, respectively, contained E. tiliae DNA, whereas 60.8 % of adult A. nemoralis tested positive for aphid DNA. Incorporating insect densities revealed that the density of H. axyridis larvae had a strong negative effect on the likelihood of detecting aphid DNA in A. nemoralis. Prey overlap for E. tiliae was widespread in space (2–13 m height in tree crowns) and time (May–October 2011) which suggests that interspecific exploitative competition, mediated by predator life-stage, more so than IGP, is an important indirect trophic interaction between co-occurring H. axyridis and A. nemoralis. Whether exploitative competition equates to displacement of A. nemoralis populations requires further investigation. Our results emphasize the need to incorporate indirect interactions in studies of insect communities following invasion, not least because they potentially affect more species than direct interactions alone.     

Determining the effects of life stage,shared prey density and host plant on intraguild predation of a native lacewing (<Emphasis Type="Italic">Chrysoperla carnea</Emphasis>) by an invasive coccinellid (<Emphasis Type="Italic">Harmonia axyridis</Emphasis>)

Negative impacts of non-native Harmonia axyridis (Pallas) on members of the native aphid enemy guild have been widely hypothesised but mainly only assessed with other coccinellid species, and mostly in small experimental arenas. Here we investigated the interactions between H. axyridis and Chrysoperla carnea Stephens larvae. In small-scale (Petri dish) arenas 2nd-instar C. carnea were at risk of predation from larval (2nd and 4th-instar) and adult (male and female) H. axyridis while 3rd-instar C. carnea were only at minimal risk from 4th-instar and adult female H. axyridis. Plant species, aphid species and aphid density did not affect intraguild predation of 2nd-instar C. carnea by 4th-instar and adult H. axyridis in mesocosm experiments. Chrysoperla carnea consumed similar numbers of Megoura viciae Buckton, Aphis fabae Scop. and Acyrthosiphon pisum Harris aphids while H. axyridis consumed fewer M. viciae than the other two species. The greatest suppression of A. pisum was achieved in treatments with both C. carnea and H. axyridis. Life stage and the sex of H. axyridis as well as the life stage of C. carnea are important variables affecting intraguild predation and these attributes should be considered when assessing the potential threat of other potentially invasive alien predators.     

<Emphasis Type="Italic">Harmonia axyridis</Emphasis> failed to establish in the Azores: the role of species richness,intraguild interactions and resource availability

To understand the role of native ladybird biodiversity in habitat susceptibility on the establishment and spread of Harmonia axyridis Pallas (Coleoptera: Coccinellidae), we characterized and compared European communities where they had established and where they had not established. The local communities of ladybirds were characterized in terms of biodiversity, the average difference in body mass between H. axyridis and other coccinellid species and the rarefied total body mass of all individuals (as a surrogate for aphid abundance and availability). The lack of success of H. axyridis in the Azores, as well as its low success in Southern Europe, can be explained by a combination of resource availability and intraguild competition. We suggest the success of this invasive alien species to establish in a habitat depends first on resource availability and second when most direct competitors for limited resources are absent or are uncommon.     

Spatio-temporal variation of strawberry aphid populations and their parasitoids

Aphids are common herbivores in the strawberry crop that can reduce plant vigor and fruit quality and also transmit viruses. Aphid species prefer diverse plant organs, which represent particular habitats of different quality for aphids and for the development of natural enemies’ populations. Different habitat units (young leaves, mature leaves, buds, flowers) of strawberry were sampled fortnightly during all seasons. We identified seven aphid species, namely Chaetosiphon fragaefolii, Aphis gossypii, and Macrosiphum euphorbiae, the most abundant. During the autumn, C. fragaefolli and M. euphorbiae were scarce and A. gossypii was denser on mature leaves, while during summer M. euphorbiae was absent. During the winter, C. fragaefolii predominated on buds and young leaves, A. gossypii on flowers, and both species on mature leaves. During the spring, C. fragaefolii was even more abundant on buds, A. gossypii predominated on mature leaves, and the three species were equally abundant on flowers and young leaves. Parasitoids emerged from A. gossypii, M. euphorbiae and Myzus persicae, but not from C. fragaefolii. Three Aphidius and two Aphelinus species were recovered. All primary parasitoid species emerged from A. gossypii, and secondary parasitoids emerged only from this aphid. Aphis gossypii parasitism on mature leaves was markedly higher in winter and summer than in autumn and spring. Parasitism of A. gossypii was independent of its density, and the number of parasitized aphids was never higher than six. Our results contribute to define the most appropriate sample unit to estimate aphid density of different species and provide information about seasonal natural parasitism.     

Combining plant resistance and a natural enemy to control <Emphasis Type="Italic">Amphorophora idaei</Emphasis>

The European large raspberry aphid Amphorophora idaei Börner (Homoptera: Aphididae) is a virus vector of at least four plant virus complexes making it the most important aphid pest of raspberries in Northern Europe. An approach combining a bottom-up control (plant resistance) and a top-down control (an aphid parasitoid) using Aphidius ervi Haliday (Hymenoptera: Aphidiinae) was investigated in the laboratory. Aphid performance (pre-reproductive period, total reproductive output, lifespan and r _m) were compared when reared on both a susceptible cultivar and a resistant cultivar with significantly poorer performance on the resistant cultivar. Parasitoid attack behaviour increased with aphid density on both cultivars, but was significantly lower on resistant plants than susceptible plants. Aphids showed a greater tendency to drop from the plant when feeding on resistant plants compared with susceptible plants. The significance of the results is discussed in the context of possible control of the aphid using these combined methods.     

Suitability of Different Prey Aphids on the Growth,Development and Reproduction of <Emphasis Type="Italic">Chrysoperla zastrowi sillemi</Emphasis> (Esben-Petersen) (Chrysopidae: Neuroptera)

The prey preference of polyphagous predator, green lacewing (Chrysoperla zastrowi sillemi (Esben-Petersen)) was evaluated against five prey aphids viz., mustard aphid (Lipaphis erysimi), green peach aphid (Myzus persicae), cabbage aphid (Brevicorynebrassicae), black bean aphid (Aphis craccivora), spirea aphid (Aphis spiraecola) of agriculture importance and compared with eggs of Corcyracephalonica (Stainton). Lacewing larvae preferred Myzus persicae most followed by Brevicorynebrassicae. The highest growth index (8.31), larval survival (94.50 %), larval weight (10.45 mg), pupal weight (8.78 mg), faster multiplication rate (0.051) and fecundity (183.4 per gravid female) of the predator were recorded on M. persicae. However, the chrysopid reared on Corcyra eggs performed best in all biological parameters and fitness, than on aphid preys. This study explores the possibilities of selecting the most suitable prey aphid species for its exploitation as supplement for mass multiplication of chrysopid during off-season or unavailability of Corcyra eggs.     

Effect of the mycotoxin deoxynivalenol on grain aphid <Emphasis Type="Italic">Sitobion avenae</Emphasis> and its parasitic wasp <Emphasis Type="Italic">Aphidius ervi</Emphasis> through food chain contamination

We investigated the influence of the Fusarium mycotoxin deoxynivalenol on the English grain aphid Sitobion avenae (Hemiptera: Aphididae) and its parasitic wasp Aphidius ervi (Hymenoptera: Braconidae) using in vitro laboratory experiments. In this tritrophic interaction, deoxynivalenol caused lethal (declined survival) and sublethal (prolonged nymphal development and reduced reproduction) effects on S. avenae aphids and consequentially led to a decreased production of parasitoid offspring resulting from parasitized deoxynivalenol-contaminated aphids. This paper highlights that the presence of mycotoxins should be considered in environmental risk assessment tests because they may alter the efficiency of biological control agents such as parasitoids through food chain contamination.     

Fish assemblage structure in an estuary of the Atlantic Forest biodiversity hotspot (southern Brazil)

We described the fish assemblage in the estuary of the Guaraguaçu River (one of the largest tributaries of the Paranaguá Bay Estuary, located within Brazil’s Atlantic Forest Biosphere Reserve) from June 2005 to May 2006, and assessed the seasonal and spatial effects of abiotic environmental attributes on the fish assemblage structure. Despite some oscillations in salinity, the upper and lower estuaries had year-round persistent oligohaline and polyhaline conditions, respectively. Despite high species richness (55 species), the Guaraguaçu River Estuary fish community contains a few dominant taxa; 11% of the richness accounts for >60% of its density and biomass. The most abundant species (in terms of both biomass and density) was Atherinella brasiliensis. Species whose densities were most strongly associated with the upper estuary were Centropomus parallelus, Ctenogobius schufeldti, Eucinostomus melanopterus, Platanichthys platana, Trinectes paulistanus, and Eugerres brasilianus. Those whose densities were most strongly associated with the lower estuary were A. brasiliensis, Sphoeroides greeleyi, Eucinostomus argenteus, Sphoeroides testudineus, Diapterus rhombeus, and Harengula clupeola. Throughout the year, canonical correspondence analysis identified: (1) the pattern of horizontal stratification of salinity along the river as being the most important variable for explaining most of the fish fauna structure; and (2) a strong relationship between the fish fauna and the salinity gradient along the estuary. Analysis of similarity further confirmed that each estuarine zone supports a year-round persistent and relatively homogeneous fish species assemblage. Total mean density and biomass remained constant over time in each estuarine habitat, but density shifted in the most abundant species, which appears related to recruitment patterns. Such species and abundance persistence likely occurs because seasonal rainfall-induced changes in river discharge are not sufficient to significantly shift runoff and salinity and thus fish assemblage structure (species composition, density and biomass) along the estuary. Such a lack of seasonal fish fauna movement as a response to changes in river flow contrasts with other estuarine systems around the world.     

Structure of a community of testate amoebae in a sphagnum dominated bog in upper sura flow (Middle Volga Territory)

Fifty nine species of testate amoebae were found in a sphagnum moss bog located in the upper Sura flow (Volga highland). The active diversity in communities of sphagnum moss biotopes was formed by 24 species. Minimal species diversity (3 species) and maximum density of organisms were noted in the driest habitat. In the habitats with the medium humidity levels, the level of species richness was similar (13–16 species) and the total density was determined by redox characteristics of the environment: under the conditions of oxygen deficit, it was two to three times lower than in an oxidized environment. The species composition specificity in sphagnum moss biotopes was determined by the degree of humidity: in the driest habitats, Arcella arenaria predominated; in the biotopes with medium humidity, Nebela tenella and Hyalosphenia elegans; and in the most humid biotopes, Hyalosphenia papilio and Heleopera sphagni. Communities of testate amoebae differed by species composition and integral characteristics at different sphagnum moss horizons: the abundance and species richness increased with depth. The proportion of living individuals in the total number of tests was 35 to 75%.