Foliage-dwelling Arthropods Research Articles

Are evergreen mistletoes on deciduous hosts arthropod winter refugia?

ABSTRACT Deciduousness is rare among native New Zealand trees, however, non-native deciduous trees now dominate many landscapes. The native evergreen mistletoe Ileostylus micranthus parasitises many non-native deciduous trees, so may be a critically important winter refuge for foliage-dwelling arthropods in deciduous trees. We compared arthropod communities on mistletoes and their evergreen or deciduous hosts in Dunedin, Otago. Foliage samples of 19 hosts and 19 mistletoes parasitising them were collected in summer and winter. Summer samples harboured 1335 arthropods including 1216 mites (Arachnida: Acari), mostly in domatia of two hosts. Winter samples harboured 60 arthropods including 19 mites. Mites were only identified to order but the 160 non-mite arthropods recovered were identified to 26 species or morphospecies in 23 families and 11 orders. The most common non-mite arthropods on hosts were mealybugs (Hemiptera: Pseudococcidae), while bark lice (Psocoptera) were most common on mistletoes. Mistletoes hosted 13 non-mite taxa not found on hosts, which were more likely to be native than those also or only found on hosts. Significantly more non-mite arthropods were found on mistletoes in winter than on their deciduous hosts. There was no difference between mistletoes and evergreen hosts in non-mite arthropod abundance. Mistletoes on deciduous hosts supported higher non-mite arthropod taxonomic richness in winter and over both seasons than their hosts. Despite the small number of non-mite arthropods recovered, our study adds to evidence that mistletoes are important habitat refugia for arboreal arthropods during suboptimal climatic periods, which in our study was during winter on deciduous host trees.

High species turnover of arthropod communities associated with distinct vegetation patches (“heuweltjies”) in an arid shrubland

Dryland ecosystems are often characterized by their vegetation patchiness. The Succulent Karoo, a semi-arid region in South Africa is characterised by distinct vegetation patches surrounded by a homogenous vegetation matrix. These patches, locally known as heuweltjies, are naturally developed earthen mounds found throughout the region that contribute significantly to landscape heterogeneity. Arthropods are key for ecological functioning in semi-arid ecosystems. However, few studies have assessed the role that heuweltjies play in maintaining arthropod diversity in the landscape. This study investigates how arthropod abundance, species richness, beta-diversity and composition respond to heuweltjies at multiple spatial scales (biotope and site). Two sampling techniques (pitfall and vacuum sampling) were used to collect epigaeic (ground) and foliage-dwelling arthropods on heuweltjies and in the surrounding matrix, at three different sites in the Succulent Karoo during drought conditions. Heuweltjies had greater epigaeic and foliage alpha-diversity and abundance than the matrix. Additionally, epigaeic and foliage arthropod community composition were dissimilar at both the biotope and site scales. Beta diversity across the three sites was high and driven by species turnover. At the biotope scale, heuweltjie and matrix plots both showed high beta-diversity. This study took place during a prolonged drought with high plant mortality and relatively few foliage arthropods, but patterns in arthropod diversity between heuweltjies and the surrounding matrix were nevertheless still apparent. These results suggest that heuweltjies promote arthropod diversity and heterogeneity in the landscape, playing a vital role as refuges, providing food and nesting resources for various arthropod species.

A Method for Quantifying Foliage-Dwelling Arthropods

A Method for Quantifying Foliage-Dwelling Arthropods

A Method for Quantifying Foliage-Dwelling Arthropods.

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimates of density requires a method with high detection probability and a known sampling area. While most described methods provide a qualitative or semi-quantitative estimate adequate for describing species presence, richness, and diversity, few provide an adequately consistent detection probability and known or consistent sampling areas to provide an index or estimate with adequate precision to detect differences in abundance across environmental, spatial, or temporal variables. We describe how to quantify leaf-dwelling arthropods by sealing the leaves and end of branches in a bag, clipping and freezing the bagged material, and rinsing the previously frozen material in water to separate arthropods from the substrate and quantify them. As we demonstrate, this method can be used at a landscape scale to quantify leaf-dwelling arthropods with adequate precision to test for and describe how spatial, temporal, environmental, and ecological variables influence arthropod richness and abundance. This method allowed us to detect differences in density, richness, and diversity of leaf-dwelling arthropods among 5 genera of trees commonly found in southeastern deciduous forests.

Impact of management on foliage-dwelling arthropods and dynamics within permanent pastures

The restoration of biodiversity within previously improved grasslands is an important objective worldwide. In some areas farmers receive remuneration for using specific strategies but the environmental responses to them are still uncertain. This study explored the short and long-term impacts of sheep grazing and/or hay cutting on arthropod foliage communities and flora within Welsh upland permanent pastures (UK). We measured arthropod abundance and diversity plus sward surface height, flower numbers and percentage of forbs and grasses. Data were collected during summer; twice before hay cutting and once shortly after. Total arthropod abundance was higher in grazed plots (due to Symphypleona flourishing) and family richness in hay cut plots, but taxa-specific responses occurred. Short-term effects reflected phenological changes (e.g. in Symphypleona or Cantharidae) and arthropod reductions after hay cut, when mostly Diptera remained. Arthropod communities were more abundant and diverse in flower-rich and forb-dominated plots managed by hay cutting and by hay cutting with aftermath grazing, although certain groups flourished in grazed only grass-dominated plots. The two managements based on a hay cut provided more heterogeneous environmental conditions than other management treatments, and these supported more diverse arthropod communities. The results make a valuable addition to the evidence base on which to base future land use policy at a time when trade-offs between agricultural production and nature conservation are under scrutiny across Europe.

Responses of grassland arthropods to an invasion by nonnative grasses

In grassland ecosystems, invasions by nonnative grasses typically decrease floristic diversity and structural heterogeneity in ways that alter the quantity and quality of habitat for animals. Grassland arthropods that rely directly on herbaceous plants for food, shelter, or as substrates for reproduction are especially vulnerable to these invasions because many have evolved specialized relationships with host plants that might be displaced. We evaluated how invasions by nonnative grasses affected abundance and richness of foliage-dwelling arthropods in semidesert grasslands of Arizona, USA. On 90, 3.1-ha plots established along a gradient of invasion where dominance of nonnative grasses ranged from 0 to nearly 100% of grass cover, we captured > 90,000 arthropods from 11 orders during 270 surveys in 2014 and 2015. Although the invasion by nonnative grasses (primarily Eragrostis lehmanniana and secondarily E. curvula) increased the amount of herbaceous foliage available to arthropods, richness of arthropods decreased by an average of 2% and total abundance by an average of 7% for every 10% increase in nonnative-grass dominance. Responses to the plant invasion, however, varied among taxa and functional groups. As dominance of nonnative grasses increased, abundances of most predators and specialist herbivores decreased, whereas abundances of most generalist herbivores were lowest at intermediate points of the invasion gradient. The changes we observed in the arthropod community have potential to alter broad-scale ecological processes, including energy flow and nutrient cycling, and to reduce food resources for insectivores, which can have adverse, cascading effects on imperiled grassland ecosystems.

Food Availability, Foraging Behavior, and Diet of Autumn Migrant Landbirds in the Boise Foothills of Southwestern Idaho

Abstract. Food availability and acquisition are critical components of a stopover site's suitability, but we know relatively little about how changes in food availability affect the stopover ecology of migrating landbirds. We examined fruit and arthropod availability in three habitats, studied foraging behavior and diet, and investigated use versus availability for passerines migrating through southwestern Idaho in autumn. Hemiptera dominated foliage-dwelling arthropod communities in all three habitats, whereas Hymenoptera were most numerous among ground-dwelling arthropods. Mountain shrubland had relatively high biomass of both ground-dwelling and foliage-dwelling arthropods, whereas conifer forest had high biomass of foliage-dwelling arthropods only and shrubsteppe had high biomass of ground-dwelling arthropods only. Species' foraging behavior varied, but most species foraged in mountain shrubland more often than expected by chance. Diets of most species included a high proportion of certain Hemiptera a...

Bats at risk? Bat activity and insecticide residue analysis of food items in an apple orchard

Although bats are reported as being threatened by pesticides, they are currently not considered in European Union pesticide risk assessments. The reason for that contradiction is probably related to the scarcity of information on bat activity in pesticide-treated fields and the pesticide residues on their food items. The authors recorded bat activity and measured pesticide residues on bat-specific food items following applications of two insecticides in an apple orchard. High activity levels of the common pipistrelle bat, a foraging habitat generalist, were detected. Airborne foragers and bats that take part of their food by gleaning arthropods from the vegetation were recorded frequently. The initial value and the decline of pesticide residues were found to depend on the arthropod type, their surface to volume ratio, their mobility, and the mode of action of the applied pesticide. The highest initial residue values were measured on foliage-dwelling arthropods. By following the toxicity-exposure ratio approaches of the current pesticide risk assessment, no acute dietary risk was found for all recorded bat species. However, a potential reproductive risk for bat species that include foliage-dwelling arthropods in their diet was indicated. The results emphasize the importance of adequately evaluating the risks of pesticides to bats, which, compared to other mammals, are potentially more sensitive due to their ecological traits.

Arthropod Abundance and Seasonal Bird Use of Bottomland Forest Harvest Gaps

We investigated the influence of arthropod abundance and vegetation structure on shifts in avian use of canopy gap, gap edge, and surrounding forest understory in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. We compared captures of foliage-gleaning birds among locations during four periods (spring migration, breeding, post-breeding, and fall migration). Foliage arthropod densities were greatest in the forest understory in all four seasons, but understory vegetation density was greatest in gaps. Foliage-gleaning bird abundance was positively associated with foliage-dwelling arthropods during the breeding (F = 18.5, P < 0.001) and post-breeding periods (F = 9.4, P = 0.004), and negatively associated with foliage-dwelling arthropods during fall migration (F = 5.4, P = 0.03). Relationships between birds and arthropods were inconsistent, but the arthropod prey base seemed to be least important during migratory periods. Conversely, bird captures were positively correlated with understory vegetation density during all four periods (P < 0.001). Our study suggests high bird abundance associated with canopy gaps during the non-breeding period resulted less from high arthropod food resource availability than from complex understory and midstory vegetation structure.

Monitoring Red Imported Fire Ant (Hymenoptera: Formicidae) Foraging Behavior and Impact on Foliage-Dwelling Arthropods on Soybean Produced Under Three Ant Suppression Regimes

The red imported fire ant, Solenopsis invicta Buren, has been reported to contribute to the biological control of key arthropod pests in soybean, Glycine max (L.) Merrill, and other crops. Solenopsis invicta also has been implicated as a major disrupter of biological control and a direct crop pest associated with reduced yields. In 2000 and 2001, fire ant foraging, survival of sentinel lepidopteran eggs and pupae, seasonal abundance of common foliage-dwelling soybean arthropods, and crop yield were assessed under three different fire ant suppression treatments at two test sites in Tift Co., GA. The treatments included an untreated control, hydramethylnon ant bait, and hydramethylnon bait in combination with the broad spectrum insecticide chlorpyriphos. Fire ant foraging was reduced in the chemically-treated plots in comparison to the control, based on fire ant numbers on hot dog baits after a 1-h field exposure in the early morning. Survival of soybean looper, Pseudoplusia includens Walker, eggs in 2000 and corn earworm, Helicoverpa zea Boddie, eggs in 2001 was lower in the untreated plots after a 24-h field exposure, where S. invicta foraging rates were high. Soybean looper pupal survival was 34 and 88% lower on foliage and the ground, respectively, in the control compared to those with reduced fire ant foraging. The seasonal abundance of foliage-dwelling soybean arthropods was primarily unaffected by the fire ant suppressing treatments. However, in 2001, green cloverworms, Hypena scabra F., and spiders were significantly lower (38.6 and 40.5%, respectively) in the chlorpyriphos plus hydramethylnon bait treatment in comparison to the other treatments. Season-long suppression of fire ants had no effect on soybean yield. The results of this study suggest that S. invicta, at naturally-occurring levels, is an active predator on some common soybean lepidopteran pests.

Foliage-dwelling arthropods in Bt-transgenic and isogenic maize: a comparison through spider web analysis

Theridion impressum is one of the dominant foliage dwelling spider species of maize fields in Hungary. Spider webs were collected from Bt and isogenic maize plots in three successive years. Captured insects in the web were identified. The most frequent prey items were aphids, plant hoppers and beetles. Although the number of captured insects in web samples from isogenic maize was slightly higher than those from Bt maize in the case of almost each insect order, except for two samples (Sternorrhyncha, 2001; Neuroptera, 2002), the differences between Bt and isogenic samples were not significant.

Field Evaluation of the Impact of Corn Rootworm (Coleoptera: Chrysomelidae)–ProtectedBtCorn on Foliage-Dwelling Arthropods

A 3-yr field study was conducted in Monmouth, IL, to evaluate the effect of transgenic Bt corn expressing a Cry3Bb1 protein (MON 863) on foliage-dwelling arthropods. The study employed a split-plot design with MON 863 corn and a conventional non-Bt near isoline (RX670) as the main plots and insecticide regimens (no insecticide, imidacloprid applied as seed treatment, tefluthrin applied as soil treatment, and permethrin applied as foliar treatment) as subplots. Foliage-dwelling arthropods were sampled with sticky traps during each of the 3 yr (2000–2002). The most abundant taxa collected included corn pests, such as Diabrotica virgifera virgifera LeConte and Chaetocnema pulicaria Melsheimer (Coleoptera:Chrysomelidae), and Rhopalosiphum maidis Fitch (Homoptera:Aphididae). The most abundant generalist predators captured by sticky traps were Coccinellidae (ladybird beetles), Nabidae (damsel bugs), Orius insidiosus Say (minute pirate bugs), Syrphidae (flower flies), Chrysoperla carnea Stephens (green lacewings), Macrocentrus cingulum Rienhardt (a braconid parasitoid), and Araneae (spiders). MON 863 corn had no consistent adverse impact on the relative abundance of any nontarget foliage-dwelling arthropod taxon, including predators and parasitoids. However, insecticide applications of foliar insecticide (permethrin) significantly and consistently decreased the abundance of ladybird beetles, green lacewings, and damsel bugs compared with the insecticidal seed treatment or no insecticide application. The abundance of the pest R. maidis also was observed to increase in the foliar-applied insecticide treatment. Therefore, adoption of MON 863 and the concurrent reduction in broad-spectrum foliar-applied insecticide use for control of adult Diabrotica spp. have the potential to enhance biological control within corn agro-ecosystems.

Field Evaluation of the Impact of Corn Rootworm (Coleoptera: Chrysomelidae)–Protected &lt;I&gt;Bt&lt;/I&gt; Corn on Foliage-Dwelling Arthropods

Abstract A 3-yr field study was conducted in Monmouth, IL, to evaluate the effect of transgenic Bt corn expressing a Cry3Bb1 protein (MON 863) on foliage-dwelling arthropods. The study employed a split-plot design with MON 863 corn and a conventional non-Bt near isoline (RX670) as the main plots and insecticide regimens (no insecticide, imidacloprid applied as seed treatment, tefluthrin applied as soil treatment, and permethrin applied as foliar treatment) as subplots. Foliage-dwelling arthropods were sampled with sticky traps during each of the 3 yr (2000–2002). The most abundant taxa collected included corn pests, such as Diabrotica virgifera virgifera LeConte and Chaetocnema pulicaria Melsheimer (Coleoptera:Chrysomelidae), and Rhopalosiphum maidis Fitch (Homoptera:Aphididae). The most abundant generalist predators captured by sticky traps were Coccinellidae (ladybird beetles), Nabidae (damsel bugs), Orius insidiosus Say (minute pirate bugs), Syrphidae (flower flies), Chrysoperla carnea Stephens (green ...

Spider web survey or whole plant visual sampling? Impact assessment ofBtcorn on non-target predatory insects with two concurrent methods

Impact assessment studies rely on relevant sampling methods. Correct evaluation of methods can be done by their concurrent use in the same sampling site and period. Collecting webs of Theridion impressum L. Koch (Araneae: Theridiidae) may serve as an arthropod sampling method: empty cuticles of prey items remain attached to the back side of the leaves with adhesive silk. Our study aimed to compare the applicability of the two methods concurrently (spider web survey and whole plant visual sampling) in a risk assessment study. The spider web survey recorded more predatory insect families than the whole plant visual sampling. Both methods were able to detect significant differences in the quantity of predatory insects in Bt vs. isogenic plots, but not in the same taxa (Nabidae: spider-web, 2001, Bt > Iso; Coccinellidae: plant sampling, 2001, Iso > Bt; Welsh-test, P < 0.05); thus, they could not confirm each other. The lack of confirmation can be explained by differences in the sensitivity and selectivity of the two methods. A web survey of T. impressum has the practical advantage that although we concentrate only on the one species during field sampling, we gain additional information on a wide range of foliage-dwelling arthropods. Due to several biological uncertainties, interpretation and explanation of the results remain problematic. Thus, additional research--based on in-situ observation and recording of T. impressum-prey interactions--is necessary before we could propose web survey method as a complementary tool in ecological impact assessment.

Target and non-target impacts from diazinon applied against &lt;i&gt;Dasineura mali&lt;/i&gt; in a Canterbury apple orchard

The control of apple leafcurling midge (Dasineura mali) with diazinon was investigated as part of an Integrated Fruit Production programme. A soil drench was applied against the emerging adults of the first generation (pre-flowering), and compared with a foliar application against the second generation (early December). Nontarget effects on the biodiversity of ground dwelling arthropods were examined using pitfall traps before and after diazinon applications, and on arboreal diversity using brushed leaf samples. Drench, foliar spray, and a combination of these treatments, all reduced percentage of damaged shoots compared to untreated plots. Drench and foliar applications gave similar results. Little impact on ground-dwelling arthropod biodiversity was detected following the drench or foliar applications. The biodiversity of foliage-dwelling (mainly beneficial) arthropods showed a significant reduction after foliar treatment.

Variation in the species composition and mean body size of an avian foliage-gleaning guild along an elevational gradient: correlation with arthropod body size.

The composition of an avian foliage-gleaning guild was analyzed with respect to body size at nine sites along an elevational gradient in the Oregon Cascades. Mean body size decreased from 20.5 g near the lower forest boundary where it meets the grassland at about 775 m to 9.3 g near timberline at about 1720 m. Both the loss of larger species and the gain of smaller species contributed to the change. Mean volume of the foliage-dwelling arthropods also decreased with increasing elevation by two orders of magnitude along the same gradient. A significant decrease in body size occurred in three arthropod groups, larval Lepidoptera, Homoptera, and spiders, and of these, larval Lepidoptera dominated the overall size trend among arthropods. Both developmental differences (higher elevation sites are delayed seasonally on the same calendar date) and taxonomic differences contributed to the change in mean arthropod size. Mean bird size was positively correlated (r=0.93) with the body size of foliage-dwelling arthropods. A similar pattern was suggested for other avian guilds dependent directly or indirectly upon foliage-dwelling arthropods, but not for guilds independent of foliage-dwelling arthropods.

Technical Note: Folding Beating-Box for Dislodging Foliage-Dwelling Arthropods for Sampling

Technical Note: Folding Beating-Box for Dislodging Foliage-Dwelling Arthropods for Sampling

Trophic Organization of Understory Birds in a Malaysian Dipterocarp Forest

Abstract Single-sample studies suggested that understory flowers and fruits and their avian consumers are scarce in the Malaysian rain forest as compared with African and Central American rain forests. Results from my longer-term studies at Pasoh Forest Reserve (Negeri Sembilan, Peninsular Malaysia) established that flowers and fruits were consistently rare as food for birds. A comparison of two forest types at Pasoh revealed the effect of lower food availability on avian trophic organization. Food resources (e.g. flowers, fruits, arthropods) were less abundant in the regenerating than in the virgin forest, and bird species richness and individual abundance were also lower in the regenerating forest understory. However, the two forests did not differ significantly in the relative importance of the various foraging guilds, suggesting that similar types of resources were present in similar proportions. None of the birds sampled in the Malaysian rain-forest understory was a specialized consumer of understory flowers or fruit, whereas birds feeding mainly on foliage-dwelling arthropods were abundant and were represented by many species. This trophic organization is contrary to that reported for rain forests in other tropical regions but may simply reflect an allocation of harvestable productivity that is different rather than lower.