Die ökologische Bedeutung der Spinnen in Forst-Ökosystemen,eine Literaturzusammenstellung

The most important literature on the ecological importance of spiders for forest ecosystems was compiled and analyzed. Forest spiders normally live in densities of 50 to 200 individuals/m² and prey, at least in Europe, predominantly on small soft-bodied insects (Diptera and Collembola mainly). However, bigger insects, including various forest pests, are also found in their prey. According to the present stand of knowledge the spiders of the soil surface seem to be important insect predators, whereas the ecological importance of spiders living on the trees is still controversial.     

Spinnen als Prädatoren von landwirtschaftlich schädlichen Blattläusen

Direct observations in grasslands and cereal fields near Zurich (Switzerland) have shown that aphids constitute an essentiel component in many spiders' prey. Spiders were observed to be predators of the agricultural harmful aphidsRhopalosiphum padi L.,Sitobion avenae F.,Metopolophium dirhodum Walck.,Hyalopterus pruni Geoffr.,Myzus persicae Sulz. andAphis fabae Scop.     

Freilanduntersuchungen zur Nahrungsökologie der Spinnen: Beobachtungen aus der Region Zürich

Zusammenfassung Von 1974–1980 wurden in der Umgebung von Zürich (Schweiz) Beobachtungen über die Nahrungsökologie von Spinnen durchgeführt. Die Resultate lassen sich wie folgt zusammenfassen: Sämtliche untersuchten Spinnenarten fraßen ausschließlich an Evertebraten (Insecta, Arachnida, Isopoda, Myriapoda, Lumbricidae). Bei den meisten untersuchten Spinnen bestand die Nahrung zu>90% aus Insekten. Kleine Fluginsekten (Dipteren, Blattläuse) stellen für zahlreiche Spinnen der Vegetationsschicht die Hauptnahrungsquelle dar. Kleine, weichhäutige Insekten (Collembolen, Blattläuse, Dipteren) sind die Nahrungsbasis der dominanten Spinnen der Bodenoberfläche. Ein vom Durchschnitt abweichendes Beutespektrum besitzen die ArtenArgiope bruennichi (Prädator von Heuschrecken u. Bienen),Xysticus cristatus (epigäisch: Prädator von Ameisen u. Spinnen),Achaearanea riparia (Prädator von Amesien u. Käfern),Coelotes terrestris (Prädator von Käfern),Pholcus phalangioides (Prädator von Asseln, Spinnen, Opilioniden etc.). Die untersuchten Spinnenarten weisen unterschiedlich breite Nahrungsspektren auf. So ist beispielsweise das Nahrungsspektrum bei den Trichterspinnen der GattungAgelena weit aufgefächert (polyphag). Im Vergleich dazu hat die TrichterspinneC. terrestris ein enges Beutespektrum (oligophag). Während bei den meisten Spinnenarten die Beutegröße der Räubergröße angepaßt ist (Beutegröße Räubergröße), erlegen einige Spinnenarten (v. a. Familien Thomisidae und Theridiidae) gelegentlich Beutetiere, die größer als sie selber sind. Die Spinnen sind überwiegend Sekundärkonsumenten innerhalb von Herbivoren-Nahrungsketten. Die auf Waldböden lebenden Wolfspinnen greifen zusätzlich auch in Detritus-Nahrungsketten ein. In Flußuferbiotopen ernähren sich Skorpionsfliegen (GattungPanorpa) häufig von Beutetieren in Spinnennetzen (Nahrungsdiebstahl).

---

Field studies on the feeding ecology of spiders: Observations in the region of Zurich (Switzerland)

The results of studies on the feeding ecology of spiders from 1974–1980 can be summed up as follows: All species of spiders examined fed exclusively on evertebrates (Insecta, Arachnida, Isopoda, Myriapoda, Lumbricidae). In most cases, more than 90% of the food consisted of insects.Numerous spiders living in the vegetation stratum feed mainly on small flying insects, such as Diptera and aphids. The same is true for the dominant spiders living on the surface of the soil, though their prey spectrum is supplemented by Collembola and apterous aphids. Thus in the average prey spectrum of spiders small insects with a soft cuticle dominate. Exceptions are found withArgiope bruennichi, a predator of grasshoppers and bees,Agelena spp. feeding mainly on relatively large insects,Xysticus cristatus, which, when hunting on the ground, preys on ants and spiders,Achaearanea riparia, preying on ants and beetles,Coelotes terrestris, a specialized predator of beetles, andPholcus phalangioides, preying on wood-lice, spiders, opilionides etc. The prey spectra of the spider species examined vary considerably in breadth. So the food spectrum of the funnel-web spiders of the polyphagous genusAgelena is large compared to that of the oligophagousC. terrestris. Whereas in most spider species the size of their prey is relatively small or only reaches the size of the predator (size of prey size of predator), some species, mainly of Thomisidae and Theridiidae, prey at times upon prey larger than they are.Spiders are secondary consumers belonging predominantly to herbivor food chains. Wolf spiders living on forest grounds intervene also in detritus food chains. Scorpionflies (genusPanorpa) often feed on prey animals in spider webs (food robbery).

---

---

Ausgeführt mit Unterstützung durch den Schweizerischen Nationalfonds zur Förderung der Wissenschaftlichen Forschung.     

Liming alters body size distribution in a community of epigeic spiders in birch forest (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth)

Key message

Liming, an ameliorative method for acidified forest soils, affected the relative abundance of prey of ground-hunting spiders and consequently reduced densities of functionally similar species of these predators.

Context

Liming, an ameliorative method for acidified forest soils, may modify the structure of an arthropod community by altering the soil characteristics and/or the availability of food resources.

Aims

We investigated the effect of liming on the community structure of ground-hunting spiders in a birch forest.

Methods

We established six experimental birch stand plots. Each stand was exposed to one of three experimental treatments: control, 1.5 t/ha, or 3 t/ha of dolomitic limestone. We collected spiders using pitfall traps during 5 years. We characterized the community in terms of activity density, species richness, community-weighted mean body size, and functional diversity and evenness in body size. We further investigated the potential links through which the liming might affect spiders, namely soil characteristics, effect of liming on birch, and densities of potential prey.

Results

The commonly used dosage of 3 t/ha reduced densities of functionally similar species which led to the reduced functional evenness in body size and increased functional divergence in body size. Liming increased soil pH only slightly but decreased the densities of spiders’ preferred prey.

Conclusion

The liming affected the community of ground-hunting spiders, at least partially, through reduced densities of their preferred prey.

     

板栗树冠节肢动物群落的时间生态位研究

测定了板栗树冠节肢动物群落主要害虫和天敌的时间生态位，分析了各类群在时间资源序列上分布的数量特征和资源利用状况，研究了各类群之间的竞争与共存机制.研究结果表明：在害虫和天敌中分别以象甲和瓢虫类的时间生态位宽度最大，象甲和蜘蛛类的时间生态位重叠指数最大，其次为蜘蛛和瓢虫类;象甲类和瓢虫类在时间资源上分布较广，对资源具有较强的竞争作用.蜘蛛类对象甲类具有较强的跟随捕食作用.蜘蛛类和瓢虫类对时间资源具有较强的竞争作用。     

Population dynamics of herbivorous insects and potential arthropod natural enemies on Alnus species in Kabale district, Uganda

Monitoring populations of pests and their natural enemies under different management situations and seasonal weather parameters provides extremely useful information for taking preventive measures against pest outbreaks. The abundance, spatial and temporal distributions of herbivorous insects and arthropod natural enemies on Alnus species were monitored at four sites in Kabale district, Uganda between June 1999 and August 2000. Chewing insects, dominated by Coleoptera (75%), constituted the majority of insect herbivores sampled. Dominant and potentially serious pests of Alnus included Apion globulipenne, an unidentified Chrysomelidae (Coleopt. 27), Phymateus viridipes, Coloborrtics corticina and a Cacopsylla species (Homoptera: Psyllidae). Spiders were the predominant natural enemies accounting for 64% of the total natural enemies encountered, followed by parasitic Hymenoptera (30%). There were marked spatial and temporal variations in arthropod abundance. Among sites, mean abundance of total insect herbivores and total natural enemies on A. acuminata over 15 months ranged from 3.8–8.5 and 3.3–4.7 individuals per 1-m branch length respectively. Over the same period, mean number of total insect herbivores and total natural enemies on A. nepalensis that was studied at only one site were 11.9 herbivores and 4.2 natural enemies per 1-m branch length. Populations of most insect orders increased in the wet season although the greatest herbivore abundance was evident in the dry season. Further studies are necessary on the impact and management strategies of the potentially important insect pests and natural enemies on Alnus.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effects of green-tree retention on abundance and guild composition of corticolous arthropods

Corticolous, or bark-dwelling, arthropods may be useful indicators of environmental changes associated with variable-retention harvests. We studied the effects of varying levels and patterns of green-tree retention on the community composition of bark-dwelling arthropods. Arthropods were sampled with crawl traps installed on 280 live trees and 260 snags (all Douglas-fir) at three locations (experimental blocks) in the western Cascade Range of Oregon and Washington. Sampling coincided with the breeding season of the brown creeper (Certhia americana), a primary avian predator, in 2003 and 2004. Within each block, arthropods were collected in five, 13-ha experimental units—a control (uncut forest) and four treatments representing one of two levels of retention (15% vs. 40% of original basal area) and one of two spatial patterns (trees dispersed vs. aggregated in 1-ha patches). In total, 166,234 arthropods – predominantly Collembola (70%) – were collected over the course of study. With the exception of Collembola, arachnids were the most abundant arthropods (23% of individuals); spiders (Araneae) accounted for >95% of arachnids. Other common insect orders included adult Coleoptera (16%), Hemiptera (15%), and Diptera (12%). For all insects combined (excluding Collembola), activity-density (daily catch per trap, an index of abundance) was significantly greater in harvest treatments than in controls. The greatest increases were found at 15% retention—densities were 2.6 times greater than in controls and 1.8 times greater than at 40% retention. Pattern of retention did not affect abundance of most arthropod groups, although two families of spiders (Linyphiidae and Thomisidae) were more abundant in dispersed than in aggregated treatments. Traps on live trees yielded 2.2 times more arthropods than did traps on snags likely reflecting differences in food resources. A high proportion of herbivorous taxa showed negative associations with local density and basal area of overstory trees and positive associations with cover of herbs, suggesting that many corticolous arthropods originate in the understory and respond positively to increases in vegetation cover following retention harvests. The numerical dominance of Collembola and high abundance of Diplopoda also suggest important ecological ties between communities of corticolous and detrital (litter-dwelling) arthropods.     

Predatory potential of three hunting spiders inhabiting the rice ecosystems

Present study was designed to assess the prey preference behaviour of three most dominant hunting spiders [Lycosa terrestris Butt, Anwar and Tahir 2006 (Araneae: Lycosidae), Pardosa birmanica Siman 1884 (Araneae: Lycosidae) and Oxyopes javanus (Thorell 1887) (Araneae: Oxyopidae)] of rice ecosystems both in the laboratory and in the field. Two types of laboratory experiments, i.e., choice and no choice feeding, were performed using only adult male and female specimens of the spiders. No choice test showed that each of the three hunting spiders readily consumed larvae and nymphs of rice pests offered. Female hunting spiders consumed more prey compared to male hunting spiders. Results of choice feeding test indicated that L. terrestris and P. birmanica preferred nymphs of rice insect pests while O. javanus preferred larvae of rice insect pests. Results of direct observations showed that in August, dipterous insects were the most numerous rice pests consumed by L. terrestris, P. birmanica and O. javanus, comprising over 56.3, 38 and 48% of their respective diets. In contrast, in September, the proportion of dipterous insects decreased dramatically and hoppers become the most numerous pests, comprising over 50, 51 and 41% of all prey and spiders consumed by L. terrestris, P. birmanica and O. javanus, respectively. In October, aquatic Heteroptera were frequently observed in their diets. Predatory potential of these hunting spiders differed statistically in the laboratory as well as in the field. It is concluded from the results of present project that studied species of spiders could successfully be used to control insect pests of rice ecosystems.     

Effect of Rhabdias pseudosphaerocephala on prey consumption of free-ranging cane toads (Rhinella marina) during Australian tropical wet seasons

The development of biological control measures to reduce the impact of invasive species is a desired goal. Rhabdias species have recently been advocated as biological control agents for invasive anurans. This study describes a field-based approach to support laboratory results on the potential impact of the lung nematode Rhabdias pseudosphaerocephala on the prey consumption of its host, the invasive cane toad (Rhinella marina, Bufonidae). Toads were sampled from various populations in the Wet Tropics of Australia during the wet seasons of 2010 and 2012. Consumed prey items were counted in 212 cane toads and identified to class and order levels and the number of lung nematodes was counted for each toad. The number of R. pseudosphaerocephala in free-ranging cane toads affected negatively the diversity of prey items consumed, but was not related to the number of prey items or the number of ants consumed. The results suggest that infection of free-ranging cane toads by the lung nematode reduces their range of prey items. Possible reasons could be a reduced locomotor activity resulting in changes of foraging modes of infected toads which was reported from some laboratory trials. Infection of cane toads by R. pseudosphaerocephala may therefore have the potential to alter the impact of cane toads on invertebrate communities and their competition for food resources with native Australian anurans.     

Microhabitat separation between the pest aphids Rhopalosiphum padi and Sitobion avenae: food resource or microclimate selection?

Niche separation between competing species is a central issue in ecology. As two of the most important pests worldwide of cereal production, Rhopalosiphum padi primarily dominates stems and basal leaves of wheat plants, whereas Sitobion avenae is common on the upper leaves and ears. Here, we investigated this microniche separation by considering effects of food resources and microclimates on the behavior and performance of R. padi and S. avenae on tissues from individual wheat seedlings. Wheat leaves provided favorable food for both aphid species and this tissue had high free amino acid and low soluble sugar compared with wheat stems. Both species preferred microclimates in the lower area of the seedlings where humidity was relatively higher and temperatures were relatively lower. In terms of performance, R. padi was more sensitive to microclimate effects than S. avenae, while the latter species was relatively more sensitive to limiting food resources. These factors may help explain why R. padi is relatively more common on lower microhabitats of seedlings, in contrast to S. avenae, contributing to the microspatial distribution of these species more generally. This information contributes to a better understanding of the relationship between these aphids and their host plants, which may assist in control strategies targeting these aphids.

     

Feeding activity and life history characteristics of the generalist predator,<Emphasis Type="Italic"> Chrysoperla carnea</Emphasis> (Neuroptera: Chrysopidae) at different prey densities

Larvae of the common green lacewing, Chrysoperla carnea (Stephens) (Neuroptera :Chrysopidae) were fed with different densities of Hyalopterus pruni (Geoffer) (Homoptera: Aphididae) in Petri dishes under laboratory conditions. Functional response, developmental time, mortality rate and fecundity of the predator were measured. Treatments were carried out at 25±1°C, 65±5% RH and a 16L:8D photoperiod in a controlled temperature cabinet. Prey was given at densities of 5, 10, 20, 40, 80, 160 and 250 aphids per larva per day and the number of consumed prey, developmental time and mortality rate of the predator were recorded daily. Larvae of C. carnea responded to increasing prey densities with increasing food consumption and older larval stages displayed a higher rate of predation than younger ones. The behaviour of each of the three larval stages matched Hollings type II functional response. Larvae were able to complete their development in each of the seven prey densities, although increased prey densities reduced developmental time and mortality rate. Increased prey consumption in immature stages resulted in a higher net reproduction rate (R ₀) and the intrinsic rate of increase (r _m) of adult females.     

Forest management and temporal effects on food abundance for a ground-foraging bird (Catharus guttatus)

While food abundance is known to limit bird populations, few studies have simultaneously examined both temporal and habitat-related variation in food abundance for ground-foraging birds. We surveyed ground-dwelling arthropods throughout the breeding season and in three forest harvest types (clearcut, selection, and shelterwood stands managed for spruce, fir and hemlock) at the Penobscot Experimental Forest (PEF), Bradley, Maine, USA. Pitfall trapping during 2003 and 2004 was used to measure seasonal and habitat-related variation in abundance of ground-dwelling arthropod food items for hermit thrushes. Arthropods were sorted into relevant taxonomic and size class categories based on the known diet of hermit thrushes. Habitat variables included forest management type, stand-level structure and composition of tree species, and microhabitat measures in a 1 m² area around the pitfall traps. We used redundancy analysis to find stand-level and microhabitat measures that best explained variation in arthropod abundance during 2004. The majority of arthropod captures comprised three groups: ants (Formicidae, 44%), ground beetles (Carabidae, 13%), and spiders (Araneae, 11%). There was significant temporal variation in captures for many taxa. Notably, there were as many as six times more Araneae in early compared to late season samples suggesting the importance of Araneae to ground-foraging birds. Carabidae were more abundant in selection versus either shelterwood or clearcut stands on one sample date. Conversely, Formicidae and Curculionidae were more abundant in shelterwood plots on one and three sampling dates, respectively. Overall, our data provided little evidence that forest management type impacts arthropod food abundance, in stands 5–20 years post-harvest. Abundance of Carabidae was positively correlated with the number of softwoods less than 5 cm DBH and the number of hardwoods greater than 10 cm DBH, while abundance of Formicidae and Homopterans was negatively associated with these same measures. Several taxa were negatively associated with percent of the 1 m² around the pitfall that was shaded, including Araneae, Carabidae, Formicidae, and Staphylinidae. These results suggest that less-shaded forest microhabitats are important areas of increased food abundance for ground-foraging birds, regardless of forest management type or tree composition. Consequently, forest managers seeking to maximize food abundance for ground-foraging birds in managed spruce-fir forests should consider retaining some large diameter hardwood trees and use management techniques that reduce forest floor shading.     

Lepidoptera larvae as food for capercaillie chick (tetrao urogallus): A field experiment

Lepidoptera larvae are important prey for capercaillie chicks {Tetrao urogallus), but utilization varies among habitats. This field experiment investigates the effects of larval feeding behaviour, abundance and the density of bilberry (Vacciniwn myrtillus) on utilization of larvae by a group of four capercaille chicks and also tests whether chick utilization differs between wet and dry coniferous forest. In fenced plots, four hand‐raised chicks were released for a 15 min feeding period. Reduction of geometrid larvae was correlated positively with their abundance but correlated negatively with bilberry density. Geometrids had a much higher predation risk than pyralids and tortricids, probably because they are exposed while feeding, in contrast to pyralids and tortricids. Total reduction of lepidoptera was higher in wet than dry forest, probably due to a higher proportion of geometrid larvae, and lower density of bilberry in the wet forest. The manner of insect feeding and habitat type (e.g. wet and dry forest), which influence bilberry density, therefore may be important factors to consider when assessing or managing habitat quality for capercaillie chicks.     

Arthropods in coarse woody debris in jarrah forest and rehabilitated bauxite mines in Western Australia

? Coarse woody debris (CWD) is returned to Alcoa’s rehabilitated mined areas in the jarrah forest as potential vertebrate fauna habitat, however, its value for invertebrate fauna has not been investigated. We sought to determine if CWD in rehabilitated areas supported a similar arthropod fauna to that on fallen logs in the adjacent unmined jarrah forest.

? Using emergence tents, sampling from logs in 5-year old and 15-year old rehabilitated forest, and in unmined forest, yielded 2266 specimens from 187 taxa. Collembola (43% of total) and Acarina (32%) were the most abundant groups, followed by Diptera (11%), Araneae (4%) and Coleoptera (3%).

? There were no significant differences in either taxa richness or overall abundance among the three forest types. However, community composition varied significantly. Species richness from the Araneida, Coleoptera and Diptera was highest in the 5-year old rehabilitated forest, while Collembola and Acarina were better represented in the unmined forest; this was related to changes in the environment surrounding the logs as rehabilitated forest develops, and to log condition. The composition of arthropods on logs in the 15-year old rehabilitated forest was intermediate, indicating a trend of increasing similarity to the unmined forest in arthropod fauna as the rehabilitated forest ages.

? We suggest that over longer time periods, CWD in rehabilitated forest will support arthropod communities similar to those found in unmined forest. Future work should determine if returning logs to mined areas facilitates the return of CWD-dependent taxa.

     

Über das Auftreten der Getreideblattlausarten (Hom., Aphididae) in norddeutschen Weizenanbaugebieten (1974/75)

The ocurrence of the different cereal aphids (Hom., Aphididae) in Northern German wheat growing areas 1974 and 1975 In July, 1974 and 1975,Macrosiphum avenae (F.) was the most common aphid on cereal fields in Northern German wheat growing areas.Rhopalosiphum padi (L.) was less abundant, whileMetopolophium dirhodum (Wlk.) was found very seldom.R. padi infested field edges only in most cases, while this was not true for all fields infested byM. avenae.     

Abandonement of coffee agroforests increases insect abundance and diversity

Shade coffee including many tree species is known to support generally high biodiversity. Due to low coffee prices on the world market, many farmers have abandoned their farms, thereby creating a new ecosystem type, which has attracted increasing interest for biodiversity conservation. Here we used pyrethrum knockdown samples to compare the arthropod community on coffee plants of six traditionally managed coffee agroforests with those of six abandoned coffee agroforests in coastal Ecuador. We investigated eight randomly selected coffee shrubs per site, six of them inside and two at the edge. All arthropods were identified to orders and beetles to morphospecies. We additionally sampled the vegetation to test for vegetation-mediated effects on the arthropod community. The number of arthropod individuals was higher in abandoned than managed coffee, driven by the abundance of Arachnida, Blattaria, and Heteroptera, and higher in the edge than in the centre of the abandoned agroforests. Higher arthropod abundance appeared to be closely related to arthropod diversity, as shown for beetles (r = 0.79, n = 96). Contrary to expectations, predator-prey ratios in managed agroforests was as high as in the abandoned ones. In conclusion, abandonment of coffee agroforests greatly encourages arthropod communities, in particular in the habitat edges, and therefore, should be considered in landscape management for conservation.     

Combining banker plants to achieve long-term pest control in multi-pest and multi-natural enemy cropping systems

Banker plants increase biological pest control by supporting populations of non-pest arthropod species, used as alternative hosts or prey by natural enemies. Due to the specificity of trophic interactions, banker plants may not efficiently promote natural enemies with different ecologies. Yet in most cropping systems, different pest species are present together and require different biocontrol agents to efficiently control them. In the present study, we tested the combined use of two banker plants and their associated prey/host to enhance populations of the specialist parasitoid Encarsia formosa targeting the main tomato pest Bemisia tabaci, and a polyphagous ladybird Propylea japonica targeting the secondary pest Myzus persicae in tomato crops. In a laboratory and a greenhouse experiment, we measured the abundances of these four species using the Ricinus communis—Trialeurodes ricini banker plant system alone, in combination with the Glycines max—Megoura japonica system, or in absence of banker plants. We found that the first banker plant system enhanced populations of E. formosa, resulting in increased suppression of B. tabaci populations and the suppression of their outbreak in both our laboratory and greenhouse experiment. Conversely, abundances of P. japonica were not affected by this first system, but were significantly increased when the second was present. This resulted in increased control of M. persicae populations and the suppression of their early and late outbreaks. Our study demonstrates the potential for combined banker plants to provide long-term, sustainable control of multiple pests by their target natural enemies in complex agroecosystems.

     

Variation in the abundance of invertebrate predators of the green spruce aphid Elatobium abietinum (Walker) (Homoptera: Aphididae) along an altitudinal transect

Green spruce aphid Elatobium abietinum (Walker) is a major defoliator of Sitka spruce (Picea sitchensis (Bong.) Carr.) in north-west Europe and other parts of the world that have a mild and wet maritime climate. Periods of cold weather during the winter currently limit E. abietinum populations and the amount of damage, but as mean winter temperatures rise in response to global climate change, overwinter survival of the aphid is likely to improve and the risk of severe and more widespread defoliation will increase. Populations of E. abietinum are also influenced by mortality caused by generalist invertebrate predators, although the extent to which predation might modify the response of E. abietinum to climate change is unclear. In this study, the response of generalist predators to changes in environmental conditions and potential increases in E. abietinum populations was evaluated by sampling invertebrate predators in the canopy of Sitka spruce along an altitudinal gradient from 310 m to 610 m above sea-level. Variation in predator abundance was related to local climate and aphid numbers. Population densities of E. abietinum differed widely between altitudes, and showed different patterns in different years, but mean densities over the 3-year study were highest at mid altitudes. In contrast, the majority of invertebrate predators (coccinellid and cantharid beetles, syrphid larvae, brown lacewings, spiders and harvestmen) were most abundant at low altitudes. Their abundance was not correlated with E. abietinum densities, but coincided with the more favourable climatic conditions at low altitudes and the availability of alternative prey. The association of low population densities of E. abietinum with greater general abundance of invertebrate predators at low altitudes, where higher temperatures would have been expected to promote higher aphid populations, suggests that above a certain temperature regime generalist predators have the capacity to prevent E. abietinum responding to further increases in environmental temperatures and eventually cause mean population densities to decline. Consequently, increases in the activity and abundance of natural enemies need to be considered when predicting how E. abietinum might respond to climate change.     

Efficiency of extracting microarthropods from the canopy litter in a Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don) plantation: a comparison between the washing and Tullgren methods

We compared the efficiency of washing versus the Tullgren method for extracting microarthropods from dead leaves and branches in the canopy of Cryptomeria japonica trees. Oribatida and Collembola were consistently the numerically dominant taxa of microarthropods, but the relative abundance differed between the two extraction methods. Oribatida accounted for more than 70% of all the microarthropods collected by the washing method but less than 30% by the Tullgren method. Collembola accounted for less than 10% collected by the washing method but about 60% by the Tullgren method. The density of Oribatida was higher when collected by the washing method than by the Tullgren method, and vice versa for the density of Collembola. Our results suggest that the washing method is appropriate for collecting Oribatida and other microarthropods, whereas the Tullgren method is better for collecting Collembola from the canopy litter of C. japonica trees.     

Source,distribution and abundance of macroarthropods on the bark of longleaf pine: potential prey of the red-cockaded woodpecker

Arthropod diversity, abundance and biomass on 50–70-year-old longleaf pine (Pinus plalustris) tree boles were examined to determine the origin of the prey available to the endangered red-cockaded woodpecker (Picoides borealis) and the variability of this prey over time. Traps designed to capture arthropods crawling on the bark (crawl traps), alighting on the bark (flight traps), and crawling on the ground (pitfall traps) were operated continuously for 12 months. Flight and crawl traps were placed at different heights. One-half of the trees with crawl traps were fitted with a barrier to prevent arthropods from crawling up from the ground. Arthropods were identified to genus from one weekly sample per month and subsamples were oven-dried and weighed to estimate biomass. The arthropod community on the bark included over 400 genera. Crawl trap captures were the most similar to the prey of P. borealis. Arthropod fauna captured in crawl traps had a 58% similarity to pitfall trap captures and a 60% similarity with flight trap captures. Flight and pitfall trap captures had a 10% similarity. Barriers to arthropod movement up the tree reduced the arthropod biomass on the bole of the trees by 40–70%. Arthropod biomass was relatively evenly distributed over the tree, but varied seasonally with the highest biomass captured in the fall of the year. In general, the study showed that little of the arthropod biomass on the bark is in the form of arthropods that live exclusively in that habitat and that a large portion of the biomass is crawling up from the soil/litter layer.