Spiders active on snow in eastern Turkey

Abstract

At temperatures below zero in winter months, a total of 202 spiders was collected by pitfall traps from a snow-covered grassland in eastern Turkey. 16 genera and 20 species were recorded, belonging to the families Gnaphosidae, Lycosidae, Linyphiidae, Thomisidae, Theridiidae, Philodromidae, Salticidae, and Tetragnathidae.     

Diversity of insects captured by weaver spiders (Arachnida: Araneae) in the cocoa agroecosystem in Tabasco, Mexico

The aim of this work was to know the diversity of insects captured by weaver spiders in a plantation of cocoa (Theobroma cacao L.) of 6 ha in the State of Tabasco, Mexico. The study was carried out from July 2004 to June 2005 by means biweekly samples of the insects captured on the spiders webs. The total of 3,041 webs of 54 species of spiders belonging to seven families (Araneidae, Theridiidae, Tetragnathidae, Uloboridae, Pholcidae, Dyctinidae and Linyphiidae) were revised. We found 1,749 specimens belonging to 10 orders of insects, represented by 93 families, the majority of Coleoptera, Diptera and Hemiptera that constituted 74% of the identified families. The biggest number of specimens of all orders was captured by Araneidae, except of Isoptera, whose specimens were captured mainly by the family Theridiidae. The index of diversity (H'), evenness (J') and similarity (Is), applied to know the diversity of families of insects captured among families of spiders, varied from 0.00 to 3.24, 0.00 to 0.81, and 0.04 to 0.522, respectively. We conclude that there is a wide diversity of insects predated by the weaver spiders in the cocoa agroecosystem, and that there are species that can be promising for the biological control of pests.     

How to catch foliage-dwelling spiders (Araneae) in maize fields and their margins: a comparison of two sampling methods

The foliage‐dwelling spider fauna was collected in maize fields and on stinging nettles in adjacent margins in Bavaria, South Germany. Two different sampling methods were evaluated: drop cloth sampling and suction sampling. The overall catch was dominated by juvenile spiders, web‐building spiders, and spiders of the families Theridiidae, Linyphiidae, Tetragnathidae and Araneidae (in decreasing order). Field margins harboured more species than maize fields, whereas the total spider abundance was higher in the maize crop. Web‐building spiders such as Theridiidae and Linyphiidae were prominent in maize by individual numbers. Suction sampling with a small suction device proved to be a more efficient and consistent sampling method for foliage‐dwelling spiders than drop cloth sampling. Density and species richness of foliage‐dwelling spiders in maize was shown to be fairly high, implying that spiders of higher strata may play a more important role in biological control than suspected up to now.     

Interactions between citrus psylla,Trioza erytreae (Hem. Triozidae), and spiders in an unsprayed citrus orchard in the transvaal lowveld

During a two year survey, a total of 3,054 spiders represented by 21 families were sampled in an unsprayed citrus orchard in the Transvaal Lowveld. Numerically the Salticidae was the dominant family (34.4%) followed by the Theridiidae (21.9%), Thomisidae (11.9%), Araneidae (7.9%), Clubionidae (7.0%) and the Tetragnathidae (3.7%). Eighteen species of spiders were observed to prey on citrus psylla,Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), while six species trap nymphs and adults under their retreats and webs. There were significant positive correlations between the weekly psylla populations and the weekly populations of web-building spiders and wandering spiders present one to four weeks later but no significant correlation between the weekly spider populations and the weekly psylla populations present one to five weeks later. This seems to indicate that while spiders are unable to keep citrus psylla populations at acceptable low levels, they may contribute in reducing their numbers.      

Effect of forestry on the abundance and diversity of arboreal spiders in the boreal spruce forest

Spiders were sampled from spruce branches during late winter in northern Sweden, to investigate the effects of forestry on the community structure of arboreal spiders. Five lichen-rich, natural spruce Picea abies forests and adjacent mature, selectively-logged lichen-poor forests were selected as sample sites. Lichen-rich forests had over three times more spiders on the branches than the lichen-poor forests. The spider community was dominated by web spinners, i.e. the families Linyphiidae. Araneidae, Tetragnathidae and Theridiidae. Hunters, i.e. Philodromidae and Clubionidae. comprised < 3% of the individuals and > 82% of all spiders were juveniles.
Among the dominant species, only the orb-weaver Araneus nordmanni was found in all sites whereas the sheet-web spider Lepthyphantes suffusus was found in all five lichen-rich forests but only in two of the lichen-poor. Both species composition and dominance differed from spider communities in southern boreal spruce canopies. Small prey items, severe abiotic conditions and high predation pressure from birds are possible reasons why web spiders dominate the arboreal community in northern Sweden. These factors could also explain the observed shift in dominance from sheet-web spiders with large body size to those with a small body size, compared with arboreal spider communities in southern boreal forests.
Diversity indices (jack-knifing of Simpson index and Q statistic) showed a higher diversity of spiders in lichen-rich than in lichen-poor forests. The lichen-rich forest had more species and less dominance, in both rank abundance and the Berger-Parker index of dominance. However, rarefaction plots indicated no differences besides lower abundance of spiders on sampled branches in lichen-poor forests. It is suggested, that habitat structure (branch size and epiphytic lichen abundance) could be an explanation for the greater number of spiders in old, lichen-rich spruce forests.     

Flowers for better pest control? Ground cover plants enhance apple orchard spiders (Araneae), but not necessarily their impact on pests

Effects of ground cover upon arboreal spiders and their ability to control pests were studied in an apple orchard over six years. The ground cover treatments were: (1) annual and perennial flowering herbs (FLOWER), (2) regularly mowed grass (GRASS) and (3) weed-free bare ground (BAREgr) in the alleys. Spider abundance and species richness increased significantly in FLOWER compared to BAREgr, with GRASS being intermediate between the other two treatments. The effects of ground cover vegetation varied across spider guilds and individual species. The number of stalkers (Salticidae) increased sharply with the amount of vegetation in the alleys, while the increase was much less steep in ambushers (mainly Thomisidae and Philodromidae), and we found no significant difference between the treatments in space web builders (Theridiidae) and orb web builders (mainly Araneidae). The spider community was dominated by the intraguild predator Carrhotus xanthogramma (Salticidae), which showed a 3.5-fold increase in FLOWER compared to BAREgr and represented 40, 54 and 63% of the total spider abundance in BAREgr, GRASS and FLOWER treatments, respectively. The other species were less numerous and their response to FLOWER compared to BAREgr treatments ranged from a ninefold increase to a sixfold decrease. Within potential prey groups, hymenopteran parasitoids, dipterans and Auchenorrhyncha were the best predictors of spider abundance. In contrast, the abundance of apple pests was independent of spider density and showed no difference between treatments, indicating that spiders in the studied orchard had little impact on the size of the pest populations. This study demonstrates that functional traits and abundances of spider guilds and species, rather than the total spider abundance per se, might explain the success or failure of spiders in conservation biological control.     

The spider assemblage (Arachnida,Aranei) in agroecosystems of the Kuban Plain: Species composition,spatial distribution,and seasonal dynamics

During two years of observations of winter wheat fields, their margins and areas adjacent to forest shelterbelts, 139 species of spiders from 18 families and 92 genera were found using net-sweeping and pitfall trapping. In the fields proper, 87 species were recorded. The species number and species diversity decreased towards the central areas of the fields. High species diversity was recorded in the field edges but not in their central parts. Spiders of the families Philodromidae, Thomisidae, and Araneidae predominated in the herb-layer; the fractions of these families were greater in the fields than in their margins. Species of the family Salticidae were more numerous in the field edges and margins. Representatives of Lycosidae were the most common among epigeic spiders, their fraction reaching 90% in the field center. The dominant forms comprised 10% of the species and 80% of the number of individuals. Agrobionts common to the temperate zone of Europe predominated in the central part of the fields. They colonized the fields rapidly and distributed uniformly over the territory in spring, and then redistributed as the crops grew. The species for which the ecological conditions of the fields were favorable colonized the fields regardless of their size; other species were restricted to the field periphery.     

花生田蜘蛛群落的研究

在花生田共采集到蜘蛛41种,隶属于12科、27属。游猎型蜘蛛主要是狼蛛科、跳蛛科、猫蛛科和管巢蛛科的种类,所占比例较高,在春花生田为60.91％～86.21％,秋花生田为50.40％～90.36％。结网蜘蛛主要是皿蛛、球蛛、肖蛸和小型园蛛。在花生的不同生长季节有不同的优势科和优势种。春花生田的优势科是狼蛛科、皿蛛科和猫蛛科,优势种是类水狼蛛、拟环纹豹蛛、脉娲蛛、食虫沟瘤蛛和斜纹猫蛛;狼蛛科、猫蛛科和球蛛科是秋花生田的优势科、脉娲蛛、斜纹猫蛛和八斑鞘蛛为优势种。     

Diversity of predaceous arthropods in the almond tree canopy in Northeastern Portugal: A methodological approach

The almond tree is an economically important crop in Mediterranean regions. However, knowledge about the biodiversity of natural enemies that may be useful as biocontrol agents is scarce. The objectives of this work were: (i) to study the diversity of predaceous arthropods; and (ii) to establish a suitable sampling protocol for arthropods of the almond tree canopy. Between April and October of 2007 and 2008, 25 randomly selected trees were sampled in an organic almond grove located in the north‐east of Portugal using the beating technique. The specimens collected were counted and identified and the sampling protocol was established by using the accumulation curves and the seasonal richness peaks of the most abundant groups of natural enemies. A total of 1856 and 1301 arthropods were captured, respectively, in 2007 and 2008, where Araneae, Coccinellidae and Formicidae were the most abundant groups. A total of 14 families and 29 species of spiders were identified as Linyphiidae, Philodromidae, Thomisidae, Araneidae and Oxyopidae, the five most abundant families in both years. In the Coccinellidae and Formicidae communities 15 and 13 species were identified, respectively. According to taxa accumulation curves, the minimum sampling effort that provided a reliable picture of the biodiversity was established in 11 samples. Moreover, considering the seasonal richness distribution, it would be advisable to concentrate the sampling period from the beginning of July to the harvesting of almonds. This protocol might generate accurate replicate samples to estimate species richness when the effect of agricultural management is studied.     

贵州赤水桫椤自然保护区蜘蛛群落多样性分析

2008年5～10月,采用随机捕捉法、扫网法和扣管法相结合,对贵州赤水桫椤自然保护区内的灌丛、竹林、稻田等生境的蜘蛛群落结构进行了调查,共采集蜘蛛标本1937头,隶属于24科81属159种,其中以跳蛛科(38种)、园蛛科(29种)和球蛛科(23种)最多,占总量的56.6%。稻田内结网型蜘蛛数量明显少于竹林和灌丛,而游猎型蜘蛛数量则相对较多,群落稳定性较差;灌丛空间异质性大,蜘蛛数量大、种类丰富,群落稳定性强;竹林生境单一,但受人为干扰较小,地面相对干燥,结网型蜘蛛介于灌丛和稻田之间,游猎型蜘蛛则很少,但均匀度较高。3种生境蜘蛛群落结构为中等不相似,表明植被类型与蜘蛛群落结构密切相关。另外发现5～10月灌丛蜘蛛群落里肖蛸科的西里银鳞蛛Leucauge celebesiana处于优势种地位,具有较大的开发利用潜力。     

Effects of kaolin on the composition of generalist predator assemblages and parasitism of Choristoneura rosaceana (Lep., Tortricidae) in apple orchards

Abstract:  In three apple orchards, we tested how the hydrophilic kaolin clay particle film Surround WP affected the diversity of generalist arthropod predator assemblages in orchard foliage and the parasitism of the pest species Choristoneura rosaceana (Harris) (obliquebanded leafroller) (Lep., Tortricidae). In two orchards, kaolin was applied to orchard foliage once a week for 4 weeks, between mid-June and mid-July in 2004 and 2005. In the third orchard kaolin was applied to foliage twice over 2 weeks in June 2004. We quantified the proportion of larvae C. rosaceana parasitized, larval populations, and the relative abundance and assemblage composition of generalist predators (spiders and insects) in the orchards. Kaolin altered the species composition of the generalist predator assemblages and reduced the relative abundances of certain generalist predators, most notably jumping and crab spiders (Salticidae and Philodromidae), assassin bugs (Reduviidae), ants (Formicidae) and coccinellids (Coccinellidae). In contrast, the relative abundances of web-spinning spiders (Araneidae, Dictynidae, Theridiidae) were not affected. Kaolin did not affect the proportion of parasitized C. rosaceana larvae, which ranged from 24% to 47% in control and kaolin treatments, or the relative proportions of parasitoid taxa. The kaolin formulation did not affect the abundance of C. rosaceana larvae, but in one orchard, kaolin did reduce the abundance of the combined numbers of C. rosaceana and another tortricid pest, Argyrotaenia velutiana . Although kaolin does not affect parasitism of C. rosaceana , it significantly changes the composition of generalist predator assemblages in orchard foliage.     

丘陵地区果园及其边界蜘蛛群落结构的动态研究

2001年4月～10月用陷阱法对莱阳丘陵苹果园、桃园和二者边界进行了定点调查,初步鉴定该区游猎性蜘蛛群落有8科19种,其中优势种依次为狼蛛科Lycosidae、逍遥蛛科Philodromidae、蟹蛛科Thomisidae和平腹蛛科Gnaphosidae。对3个生境的蜘蛛群落研究表明,（1）各生境各季节蜘蛛群落组成不同;蜘蛛群落多样性、丰富度均有差异。（2）早春季节蜘蛛主要栖息在边界;随边界植株的长高,蜘蛛迁向两侧的苹果园和桃园中,其生态位开始分离。（3）农事操作后,边界可作为蜘蛛的保护场所聚集部分蜘蛛。通过对蜘蛛群落多样性的分析,提出了应将每年的5月和8月作为蜘蛛的重点保护时期,尤应加强边界的保护。     

Spider Fauna of Jeju Island in Korea

A critical check list of the spiders in Jeju island, Korea is presented with review of published reports from 1936 to 2001 and identification of the authors' specimens collected from 1964 to 2001. Total 166 genera 347 species belonging to 36 families of spiders was classified in Jeju Island. The species composition of spiders in Jeju island comprises about 52% of total number of Korean spider species. Dominant spider families with species abundance were Araneidae, Salticidae, Theridiidae, Linyphiidae and Lycosidae. The spider fauna of Jeju island is under strong influence of northern species which are Holarctic and Palearctic species.     

海南天然林与橡胶林蜘蛛多样性比较

为探索天然林和橡胶林蜘蛛多样性现状,于2010年8月在海南黎母山自然保护区选取天然林和橡胶林,采用扫网法、陷阱法和单位面积法收集蜘蛛标本,分析两种林型之间蜘蛛组成、多样性和功能群差异,并以蜘蛛科和数量分布为属性进行主成分分析(PCA),探讨林型中样方之间蜘蛛群落的相似性。共采集蜘蛛标本3609头,用于统计分析的成蛛969头,归属于23科,162种。天然林20科,100种,优势类群为跳蛛科、球蛛科和园蛛科;橡胶林17科,87种,优势类群为肖蛸蛛科、狼蛛科和猫蛛科。从蜘蛛的数量分布看,橡胶林蜘蛛个体密度显著高于天然林;而天然林多样性指数和丰富度指数显著高于橡胶林。橡胶林中结圆网型和游猎型蜘蛛显著高于天然林,结皿网型显著低于天然林,伏击型不存在显著性差异。PCA分析结果表明,24个样方趋于分成天然林和橡胶林2组,并且天然林样方之间相似性极高,而橡胶林样方之间相似性相对较低。以上结果表明:(1)橡胶林替代天然林后蜘蛛群落结构发生变化,多样性降低;(2)增加生境结构的复杂性和减少人为干扰对保护和恢复物种多样性有重要意义。     

Bird predation affects diurnal and nocturnal web-building spiders in a Mediterranean citrus grove

Spiders and birds can greatly decrease insect populations, but birds also limit spider densities in some habitats. Bird predation is thought to be one of the causes behind nocturnal activity in spiders, so night-active spiders that hide in retreats during the day should be less affected by bird foraging than day-active spiders. However, this hypothesis has not yet been tested. We investigated the importance of bird predation on the spider community of a Mediterranean organic citrus grove. We excluded birds by placing net cages over the trees and we conducted visual searches in the canopies to sample web-building spiders. As there are many nocturnal species in the family Araneidae, we conducted searches both by day and by night to compare the abundance of active araneids in these two time periods. We sampled the tree trunks with cardboard bands to collect hunting spiders. In bird-excluded canopies there were more spiders of the families Araneidae and Theridiidae. There were higher numbers of active Araneidae at night, but these were just as negatively affected by bird predation as day-active Araneidae, so there was no evidence of nocturnal activity serving as an anti-predator strategy. We did not find any negative impact of birds on hunting spiders. Our results contrast with other studies reporting a negative effect of birds on hunting but not on web-building spiders.     

Invasive Canadian goldenrod (<Emphasis Type="Italic">Solidago canadensis</Emphasis> L.) as a preferred foraging habitat for spiders

Invasions of alien species are a great threat to biodiversity and native species communities. There are many examples in the literature on how the invasive plants affect the natural environment. Beside reports on negative effects of these invasions, there are also several studies indicating a positive impact of the invaders. Canadian goldenrod (Solidago canadensis) is one of the most invasive plant species all over Europe. Earlier studies showed that the goldenrod affects natural plant communities and has a negative impact on many animals, both vertebrates and arthropods. However, all the studies were conducted during goldenrod flowering. In contrast, this study has tested the novel hypothesis that Canadian goldenrod has a positive effect on native spider hunting success and increases spider abundance in farmland outside the growing season. Observations were made during spring on 13 meadows: 7 invaded and 6 non-invaded by goldenrod. All tall plants from experimental plots (1 m² each) were examined for the presence of spiders, their nets and prey. Prey items were counted only in spider webs. The results support the hypothesis that S. canadensis is a favourable foraging habitat for spiders: 14.6 spiders/m² on invaded plots versus 2.2 on non-invaded ones. Many spiders of the families Theridiidae and Araneidae were found on goldenrod plants, but on native plants only the Araneidae were found. Moreover, on invaded plots, much more prey items/m² were present in spiders webs than on non-invaded plots (155.3 vs. 13.8). The study is a rare example of a positive influence of invasive plants on the native arthropod community. This is also a novel approach that shows the importance of dry goldenrod stems in invaded ecosystems.     

Oldest true orb-weaving spider (Araneae: Araneidae)

The aerial orb web woven by spiders of the family Araneidae typifies these organisms to laypersons and scientists alike. Here we describe the oldest fossil species of this family, which is preserved in amber from Alava, Spain and represents the first record of Araneidae from the Lower Cretaceous. The fossils provide direct evidence that all three major orb web weaving families: Araneidae, Tetragnathidae and Uloboridae had evolved by this time, confirming the antiquity of the use of this remarkable structure as a prey capture strategy by spiders. Given the complex and stereotyped movements that all orb weavers use to construct their webs, there is little question regarding their common origin, which must have occurred in the Jurassic or earlier. Thus, various forms of this formidable prey capture mechanism were already in place by the time of the explosive Cretaceous co-radiation of angiosperms and their flying insect pollinators. This permitted a similar co-radiation of spider predators with their flying insect prey, presumably without the need for a 'catch-up lag phase' for the spiders.     

Low metabolic rates in primitive hunters and weaver spiders

The rates of oxygen consumption and carbon dioxide release of primitive hunters and weaver spiders, the Chilean Recluse spider Loxosceles laeta Nicolet (Araneae: Sicariidae) and the Chilean Tiger spider Scytodes globula Nicolet (Araneae: Scytodidae), are analyzed, and their relationship with body mass is studied. The results are compared with the metabolic data available for other spiders. A low metabolic rate is found both for these two species and other primitive hunters and weavers, such as spiders of the families Dysderidae and Plectreuridae. The metabolic rate of this group is lower than in nonprimitive spiders, such as the orb weavers (Araneae: Araneidae). The results reject the proposition of a general relationship for metabolic rate for all land arthropods (related to body mass) and agree with the hypothesis that metabolic rates are affected not only by sex, reproductive and developmental status, but also by ecology and life style, recognizing here, at least in the araneomorph spiders, a group having low metabolism, comprising the primitive hunters and weaver spiders, and another group comprising the higher metabolic rate web building spiders (e.g. orb weavers).     

Potential predation of non-webbuilding spider assemblage on cotton pests Helicoverpa armigera and Spodoptera littoralis (Lepidoptera: Noctuidae)

The relative feeding rates and preferences of a hunting-spider assemblage inhabiting southern Spanish cotton fields for two major cotton pests, Helicoverpa armigera (Hübner) and Spodoptera littoralis (Boisdubal) (Lepidoptera: Noctuidae), were analyzed under laboratory conditions. First, a no-choice feeding test was used to determine relative feeding rates for hunting-spider families and species, offering a fixed number of 10 neonate larvae of H. armigera or S. littoralis and observing predation after 2 h, 4 h, 8 h, and 24 h. In a second test, Drosophila melanogaster, a very palatable alternative prey, was used to determine the degree of preference for cotton pest larvae. The mean number of first-instar lepidoptera larvae consumed by hunting spiders after 24 h was 8.57±0.25. As expected, spiders showed no preference for either of the two cotton pest species H. armigera and S. littoralis over the other. Results also showed that cursorial spiders of the families Miturigidae (represented here by Cheiracanthium pelasgicum) and Philodromidae consumed significantly higher percentages of larvae than crab spiders belonging to the Thomisidae family after 2 h and 24 h, respectively. In the prey choice test, Cheiracantium pelasgicum displayed a strong preference for cotton pest larvae while Thomisidae and Oxyopidae showed no significant preference. In addition, as the attack sequence progressed, Ch. pelasgicum showed a clear tendency towards the alternation of prey while Thomisidae, and more irregularly Oxyopidae, maintained their preference for D. melanogaster. These findings confirmed both the considerable potential value of some cursorial spiders (e.g. Ch. pelasgicum) in the biological control of lepidopteran cotton pests and the relatively low impact of other hunting spiders, e.g. Thomisidae, on pests of this kind.     

Composition and diversity of the spider fauna in the canopy of a montane forest in Tanzania

Spiders were sampled using insecticide knockdown in an African montane forest in the Uzungwa Mountains of Tanzania. The results are used to discuss the faunal composition at the site and in comparison to other sites, and the implications of the results for estimating spider diversity in Africa are discussed. A total of 5233 adults comprising 149 species were collected from 11 samples covering a total of 906 m² of projected area. Three species contributed 45% of the sample. Previous insecticide knockdown studies of tropical lowland forest canopies have shown a dominance of Theridiidae, Salticidae and Araneidae. In the present study Linyphiidae dominated in abundance and were the second most diverse in terms of species richness. Other abundant families were Oonopidae and Pholcidae, while Theridiidae, Salticidae and Araneidae were rich in species. This supports a previous study, which indicated that the importance of linyphiids increases with altitude. Species richness was predicted using a number of estimators, which produced relatively similar results. Using the abundance-based estimator, Chao 1, the predicted richness for the total area sampled is 183 ± 15 species. This indicates that at least 20% of the area's spider community remains unsampled. A high ratio of undescribed species (approximately 80%) and a relatively high species turnover compared to a site 20 km away within the same forest complex suggests that the number of spiders in Africa could well be much higher than the current, published estimate of 20000 species.