The phylogenetic placement of Psechridae within Entelegynae and the convergent origin of orb‐like spider webs

Evolutionary convergence of phenotypic traits provides evidence for their functional success. The origin of the orb web was a critical event in the diversification of spiders that facilitated a spectacular radiation of approximately 12 000 species and promoted the evolution of novel web types. How the orb web evolved from ancestral web types, and how many times orb‐like architectures evolved in spiders, has been debated for a long time. The little known spider genus Fecenia (Psechridae) constructs a web that resembles the archetypical orb web, but morphological data suggest that Psechridae (Psechrus + Fecenia) does not belong in Orbiculariae, the ‘true orb weavers’, but to the ‘retrolateral tibial apophysis (RTA) clade’ consisting mostly of wandering spiders, but also including spiders building less regular webs. Yet, the data are sparse and no molecular phylogenetic study has estimated Fecenia's exact position in the tree of life. Adding new data to sequences pulled from GenBank, we reconstruct a phylogeny of Entelegynae and phylogenetically test the monophyly and placement of Psechridae, and in doing so, the alternative hypotheses of monophyletic origin of the orb web and the pseudo‐orb versus their independent origins, a potentially spectacular case of behavioural convergence. We also discuss the implications of our results for Entelegynae systematics. Our results firmly place a monophyletic Psechridae within the RTA clade, phylogenetically distant from true orb weavers. The architectural similarities of the orb and the pseudo‐orb are therefore clearly convergent, as also suggested by detailed comparisons of these two web types, as well as the spiders' web‐building behaviours and ontogenetic development. The convergence of Fecenia webs with true orbs provides a remarkable opportunity to investigate how these complex sets of traits may have interacted during the evolution of the orb.     

Copulatory Mechanics in the Funnel-web Spiders Histopona torpidaand Textrix denticulata(Agelenidae,Araneae)

The functional morphology of the copulatory organs of Histopona torpida(C. L. Koch, 1834) and Textrix denticulata(Olivier, 1789), investigated by semi-thin serial sectioning after freeze-fixation of the animals in copula, is described. In H. torpida, the long embolus runs through a precisely defined course in the membraneous genital pouch of the female vulva. The patellar apophysis locks the pedipalp in the female epigastric furrow. In T. denticulatathis is accomplished by the retrolateral tibial apophysis that gets hold at the female scape. In both species the conductor has a locking as well as a guiding function for the embolus. A comparison with previously investigated agelenids shows a surprising diversity in the function of the retrolateral tibial apophysis.     

The retrolateral tibial apophysis in spiders—shaped by sexual selection?

The functional significance of the retrolateral tibial apophysis (rta) on the male pedipalps in four spider species with different mating positions is investigated with the help of histological serial sections prepared after freeze-fixing copulating pairs with liquid nitrogen. The results of this study, as well as most data in previous works, suggest that the rta is mostly used to fix the male pedipalp to the female epigyne in order to ensure the intromission of the sperm transferring embolus. This is in accordance with the female choice hypothesis on genitalia which predicts that species-specific genital structures should directly or indirectly contact the female during copulation and thus be shaped by sexual selection.     

Species-Specificity of Chemical Signals: Silk Source Affects Discrimination in a Wolf Spider (Araneae: Lycosidae)

Female spiders deposit chemical cues that elicit male courtship behavior with silk. These cues are often assumed to be species-specific although male spiders may court in response to chemical cues of closely-related species. We used behavioral assays to test the extent of species discrimination of female chemical cues by male Schizocosa ocreata, a wolf spider (Lycosidae). Discrimination, expressed as relative courtship intensity of males, varied significantly with phylogenetic distance. Males did not discriminate between female cues of conspecifics and a sibling species, S. rovneri. Courtship response was intermediate for another species within the ocreata clade and not different from control for spiders outside the clade. These findings support the sibling species status of S. ocreata and S. rovneri, and also suggest the composition of female chemical signals is conserved across closely related wolf spider species.     

蚊幼对狼蛛的营养作用研究

研究蚊子幼虫（子孓）以拟水狼蛛（Ｐｉｒａｔａｓｕｂｐｉｒａｔｉｃｕｓ）的营养,繁殖作用,结果表明狼蛛对蚊幼的捕食符合ＨｏｌｌｉｎｇⅡ型功能反应,喂以蚊幼和不喂蚊幼处理狼蛛的体重增长率和生殖有极显著差异,在相同蚊幼密度下,狼蛛初始体重越小,增长率越大,经计算狼蛛每增重１ｍｇ,需消耗１０．５８ｍｇ蚊幼,这基本符合生态系统营养级能量流动的１／１０法则,狼蛛体重大小对褐飞虱的捕食量有明显差异,体重大的个体     

Spermatozoa and spermiogenesis of the wolf spider Schizocosa malitiosa (Lycosidae, Araneae) and its functional and phylogenetic implications

The wolf spider Schizocosa malitiosa is a well-known model system for studies on sexual selection in spiders. Despite this, little is known about the morphology of the reproductive system and spermatozoa in this species. In the present study, we investigate the male genital system and sperm cells of S. malitiosa using electron microscopy and provide a computer-based 3D reconstruction of the spermatozoa for the first time for arthropods. In general, the male genital system consists of two long, tube-like testes that lead into convoluted deferent ducts. The ejaculatory duct is enlarged and contains a large quantity of sperm and secretion. As revealed by transmission electron microscopy, only one type of secretion droplet is present in the seminal fluid. The spermatozoa of S. malitiosa resemble an organization known for members of the RTA clade, i.e., with an arrow-shaped acrosomal vacuole partly sunk into the nucleus and a chambered centriolar adjunct (a newly introduced character). This organization provides further support for these characters as potential synapomorphies for the RTA clade. By the end of the spermiogenesis, the nucleus and axoneme coils within the cell and a multi-layered secretion sheath are formed representing cleistospermia. The function of the thick secretion sheath is still unknown, but might be correlated either with the residency time in the female (insemination until oviposition) since female S. malitiosa do not lay eggs before the fourth month after copulation or with the receptivity-inhibiting substances suggested for this species.     

Developmental changes in the spinning apparatus over the life cycle of wolf spiders (Araneae: Lycosidae)

Spiders are characterized by their spinning activity. Much of the current knowledge of the spinning apparatus comes from studies on orb web spiders and their relatives, whereas wolf spiders have been more or less neglected in this respect. Therefore, we studied developmental changes in the spinning apparatus of four wolf spiders (Tricca lutetiana, Arctosa alpigena lamperti, Pardosa amentata, and Xerolycosa nemoralis) throughout their life cycles. Each of these lycosids has a stenochronous life cycle, but of varied length (from 1 to 3 years) and number of instars (from seven to ten). Use of the spinning apparatus begins in the first instar, after leaving the egg sac. Secondary ampullate, all piriform, and all but four aciniform glands are tartipore‐accommodated. The tartipores, collared openings through which silk gland ducts pass during proecdysis, appear on the spinning field starting with the second instar. Tartipore‐accommodated glands can function during proecdysis and their evolution corresponds with the way spiders secure themselves when molting. We suggest that the function of aciniform silk in juvenile wolf spiders is to serve as an ancillary “scaffold” supporting the spider's body during ecdysis.     

Changes in wolf spider (Araneae) assemblages across woodland–pasture boundaries in the central wheat‐belt of New South Wales,Australia

The abundance of wolf spiders (Lycosidae) was measured across woodland–pasture boundaries in the wheat‐belt of New South Wales, Australia, to determine the nature and magnitude of any edge effect. Spiders were collected by spotlighting along sample plots in woodlands located at distances of 5, 20, 35 and 200 m from the edge, and along sample plots in paddocks located at distances of 5 and 20 m from the edge. The wolf spider assemblage changed significantly across the edge, but the difference could be accounted for only by a change between the woodland and the paddock and not by any changes within the woodland at different distances from the edge. Ground cover (wolf spider microhabitat) changed significantly between the paddock and the woodland, but there were no consistent differences in microhabitat with distance from edge within either paddocks or woodlands. There was a significant correlation between an ordination of sites based on spider species abundance and an ordination based on microhabitat variables, suggesting that the wolf spider assemblage was responding to differences in microhabitat. Fine‐scale selection of microhabitat by most wolf spider species was non‐random, with most species preferring locations with grass cover, rather than more open locations. The present study indicates that wolf spiders are mostly unaffected by edge conditions at the woodland–paddock boundary. Accordingly, small and/or linear remnants with high edge‐to‐area ratios may constitute suitable faunal habitat for wolf spiders and perhaps other terrestrial arthropod species, despite the fact that this configuration is unsuitable for many vertebrate species.     

Generalist predators in organically and conventionally managed grass‐clover fields: implications for conservation biological control

Organically managed agroecosystems rely in part on biological control to prevent pest outbreaks. Generalist predators (Araneae, Carabidae and Staphylinidae) are a major component of the natural enemy community in agroecosystems. We assessed the seasonal dynamics of major generalist predator groups in conventionally and organically managed grass–clover fields that primarily differed by fertilisation strategy. We further established an experiment, manipulating the abundant wolf spider genus Pardosa, to identify the importance of these predators for herbivore suppression in the same system and growth period. Organic management significantly enhanced ground‐active spider numbers early and late in the growing season, with potentially positive effects of plant cover and non‐pest decomposer prey. However, enhancing spider numbers in the field experiment did not improve biological control in organically managed grass–clover fields. Similar to the survey results, reduced densities of Pardosa had no short‐term effect on any prey taxa; however, spider guild structure changed in response to Pardosa manipulation. In the presence of fewer Pardosa, other ground‐running spiders were more abundant; therefore, their impact on herbivore numbers may have been elevated, possibly cancelling increases in herbivore numbers because of reduced predation by Pardosa. Our results indicate positive effects of organic farming on spider activity density; however, our survey data and the predator manipulation experiment failed to find evidence that ground‐running spiders reduced herbivore numbers. We therefore suggest that a positive impact of organic fertilisers on wolf spiders in grass–clover agroecosystems may not necessarily improve biological control when compared with conventional farming.     

Nesting habits of two spider wasps: Anoplius infuscatus and Episyron sp. (Hymenoptera: Pompilidae), with a review of the literature

Many behavioural aspects of Anoplius infuscatus (Vander Linden) and Episyron sp. Schioedte were examined in detail, both on a qualitative and, when possible, on a quantitative level, during a long-term field study in Northern Italy. Both wasps dig unicellular nests on bare soil, which are filled with a single spider to feed the brood. The main differences regard the way to hunt their prey, that of burrowing, that of transporting and introducing the spider into the nest, the habit of amputating spider legs and the abdominal movements during nest closing. On the whole, starting from prey capture to nest closure, A. infuscatus is significantly slower than Episyron. The observed ethological differences are well fitted to the exploitation of the different preys consisting in wolf spiders (Lycosidae) and orb weaving spiders (Araneidae), respectively. Some flexibility in the observed behaviour is described. A critical re-examination of the literature shows that, even if most results agree with those of previous authors, two controversial points remain open regarding Episyron species: the position of the egg (on the prey or on the cell wall) and the way to grasp the spider during tranport and introdution into the nest.     

Spinneret Microstructure of the Silk Spinning Apparatus in the Crab Spider, Misumenops tricuspidatus (Araneae: Thomisidae)

The silk spinning apparatus in the crab spider, Misumenops tricuspidatus was studied with the field emission scanning electron microscope (FESEM) and the main microstructural characteristics of the silk glands are presented. In spite of the fact that the crab spiders do not spin webs to trap a prey, they also have silk apparatus even though the functions are not fully defined. The crab spider, Misumenops tricuspidatus possesses only three types of silk glands which connected through the typical spinning tubes on the spinnerets. The spinning apparatus of Misumenops closely corresponds to that of wandering spiders such as jumping spiders or wolf spiders except some local variations. Anterior spinnerets comprise 2 pairs of the ampullates and 48 (±5) pairs of pyriform glands. Another 2 pairs of ampullate glands and nearly 20 (±3) pairs of aciniform glands were connected on the middle spinnerets. Additional 50 (±5) pairs of the aciniform glands were connected on the posterior spinnerets. The aggregate glands and the flagelliform glands which have the function of sticky capture thread production in orb‐web spiders as well as the tubuliform glands for cocoon production in females were not developed at both sexes of this spider, characteristically.     

转基因水稻表达的Bt蛋白对拟环纹豹蛛(Pardosa pseudoannulata)生长发育的影响

为明确转基因水稻表达的Bt蛋白沿捕食性食物链的传递及其对生态系统中较高营养级生物的影响,在实验条件下(28±0.5 ℃,R.H=80%,L∶D=12h∶12h)以田间优势自然天敌拟环纹豹蛛为对象,以取食转Cry1Ab/Cry1Ac基因水稻汕优63(简称Bt水稻)叶片24 h的稻纵卷叶螟幼虫为猎物饲养拟环纹豹蛛,并测定了...     

Metabolic rates during rest and activity in differently tracheated spiders (Arachnida,Araneae):<Emphasis Type="Italic"> Pardosa lugubris</Emphasis> (Lycosidae) and<Emphasis Type="Italic"> Marpissa muscosa</Emphasis> (Salticidae)

With flow-through respirometry under video tracking, the CO₂ release of adult male and female Pardosa lugubris (wolf spider) and Marpissa muscosa (jumping spider) was measured during rest and activity. Activity metabolism was measured in phases in which the animals were spontaneously active and during forced exercise. Standard metabolic rates (V_CO2/t) were 1.43 nmol s^–1 g^–1 in M. muscosa and 1.7–1.8 nmol s^–1 g^–1 in P. lugubris. Egg production caused higher resting rates in females compared with the males in P. lugubris. Maximum mass-specific CO₂ release, the additional amount of CO₂ released after activity and the factorial aerobic scope were higher in M. muscosa. Additionally, half-time recovery and the lag between end of activity and maximum CO₂ release were lower in the jumping spider. The results are consistent with the hypothesis that the well-developed tracheal system in jumping spiders increases the efficiency of the respiratory system in comparison with wolf spiders, which possess similarly developed lungs but only a simple tracheal system that is restricted to the opisthosoma.Communicated by G. Heldmaier     

Molecular phylogeny of the tropical wandering spiders (Araneae,Ctenidae) and the evolution of eye conformation in the RTA clade

Tropical wandering spiders (Ctenidae) are a diverse group of cursorial predators with its greatest species richness in the tropics. Traditionally, Ctenidae are diagnosed based on the presence of eight eyes arranged in three rows (a 2–4–2 pattern). We present a molecular phylogeny of Ctenidae, including for the first time representatives of all of its subfamilies. The molecular phylogeny was inferred using five nuclear (histone H3, 28S, 18S, Actin and ITS-2) and four mitochondrial (NADH, COI, 12S and 16S) markers. The final matrix includes 259 terminals, 103 of which belong to Ctenidae and represent 28 of the current 49 described genera. We estimated divergence times by including fossils as calibration points and biogeographic events, and used the phylogenetic hypothesis obtained to reconstruct the evolution of the eye conformation in the retrolateral tibial apophysis (RTA) clade. Ctenidae and its main lineages originated during the Paleocene–Eocene and have diversified in the tropics since then. However, in some analyses Ctenidae was recovered as polyphyletic as the genus Ancylometes Bertkau, 1880 was placed as sister to Oxyopidae. Except for Acantheinae, in which the type genus Acantheis Thorell, 1891 is placed inside Cteninae, the four recognized subfamilies of Ctenidae are monophyletic in most analyses. The ancestral reconstruction of the ocular conformation in the retrolateral tibial apophysis clade suggests that the ocular pattern of Ctenidae has evolved convergently seven times and that it has originated from ocular conformations of two rows of four eyes (4–4) and the ocular pattern of lycosids (4–2–2). We also synonymize the monotypic genus Parabatinga Polotov & Brescovit, 2009 with Centroctenus Mello-Leitão, 1929. We discuss some of the putative morphological synapomorphies of the main ctenid lineages within the phylogenetic framework offered by the molecular phylogenetic results of the study.     

Consumptive and non‐consumptive effects of wolf spiders on cucumber beetles and cucumber plant damage

Biological control research often focuses on the ability of predators to reduce pest densities and protect crops through consumption. Less studied is their ability to protect crops by altering pest behaviour (non‐consumptive effects). Lab experiments were conducted to test predation rates of striped cucumber beetles (Acalymma vittatum; Coleoptera: Chrysomelidae) and spotted cucumber beetles (Diabrotica undecimpunctata howardi; Coleoptera: Chrysomelidae) by large (>10 mm) wolf spiders (Araneae: Lycosidae). Field experiments were conducted to examine how the physical presence and/or cues of spiders impact the behaviour and mortality of A. vittatum (specialist) and D. undecimpunctata (generalist) cucumber beetles as well as growth and damage of cucumber plants (Cucumis sativus; Cucurbitaceae). A. vittatum and D. undecimpunctata adults were added to caged cucumber plants without a spider, with spider cues only (spider removed before beetle inclusion), with spider only (spider introduced to plants immediately before beetle inclusion), and with spiders and their cues present (spiders introduced 24 hr in advance of beetle inclusion). A. vittatum responded to spider cues primarily by emigrating from plants. Contrarily, D. undecimpunctata did not display obvious responses, such as reduced feeding or increased emigration, to spider foraging and/or cues. Actively foraging lycosids increased A. vittatum mortality and reduced densities of D. undecimpunctata in the field when cucumber plants were flowering. This study highlights how non‐consumptive and consumptive effects can play a role in modifying pest populations, and how these effects can vary across species and plant growth stages.     

Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae,Mygalomorphae, Nemesiidae)

We describe two new species of the nemesiid spider genus Chaco from Rocha Province, Uruguay. These new species are diagnosed based on genital morphology, male tibial apophysis spination, and burrow entrance. We test cospecificity of one species, Chaco costai,via laboratory mating experiments. The new species are diagnosed and illustrated and habitat characteristics, and capture behavior are described. We conduct a cladistic analysis based on a previously published morphological character matrix that now includes the newly described species.     

Intra-guild predation relaxes natural enemy impacts on herbivore populations

Abstract. 1. To investigate the role of intra-guild predation in mediating the impact of the natural enemy complex on herbivore populations, a manipulative field experiment was conducted using uncaged plots (islets of Spartina cordgrass) on a North American salt marsh. The densities (moderate or low) of two invertebrate predators, the generalist wolf spider Pardosa littoralis and the specialist mirid bug Tytthus vagus , were manipulated in a 2 × 2 factorial design, and the resulting treatment effects on the population growth of their herbivorous prey, Prokelisia planthoppers, were assessed.
2. The abundance of wolf spiders on experimental islets was unaffected by the presence of mirid bugs, however the density of mirid bugs was influenced very negatively by the presence of the wolf spider.
3. The negative effect of the wolf spider on mirid bugs most probably resulted from the intra-guild predation of mirids by spiders because planthopper limitation by the wolf spider alone was significantly greater than when both predators were present.
4. As a result of intra-guild predation, planthopper population growth was positive in the presence of both predators, despite the fact that each predator alone promoted a decrease in planthopper population growth.
5. Notably, the occurrence of intra-guild predation diminished top-down impacts on planthopper populations in a relatively simple food web where strong top-down effects were expected. This result, however, was limited to habitats on the marsh with simply structured vegetation lacking leaf litter.     

Parallel phenotypic evolution in a wolf spider radiation on Galápagos

Within island archipelagos, repeated ecological settings may lead to radiations wherein similar niches are recurrently occupied. Although it has been shown that species with common habitat requirements share particular traits, it remains relatively unexplored to what extent this may lead to the repeated evolution of almost identical phenotypes (phenocopies) and how this correlates with traits subjected to sexual selection. Exploring divergence patterns of ecological and sexual relevant traits within spiders seem promising to enhance our understanding of the relative role of natural and sexual selection. Here, we conduct a detailed morphological analysis on a large set of genital and non‐genital traits (morphometrics, colour pattern) within a radiation of the wolf spider genus Hogna Simon, 1885 on Galápagos and interpret these data, taking into account their known phylogenetic relationship. Our results show that recurrent environmental gradients have led to the parallel evolution of almost identical phenotypes, which not only proves that natural selection has driven morphological divergence, but also suggests that a similar genetic or developmental basis most likely underlies this divergence. Among‐species variation in genital traits in contrast rather reflects the phylogenetic relationships on Santa Cruz and San Cristóbal. The combination of these data indicate that speciation in this system is driven by the combined effect of ecological mechanisms and allopatric divergence in sexual traits. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 123–136.     

Copulatory Mechanism in Holocnemus pluchei and Pholcus opilionoides,With Notes on Male Cheliceral Apophyses and Stridulatory Organs in Pholcidae (Araneae)

Huber, B. A. 1994. Copulatory mechanism in Holocnemus pluchei and Pholcus opilionoides, with notes on male cheliceral apophyses and stridulatory organs in Pholcidae (Araneae).—Acta Zoologica (Stockholm) 76: 291–300. The pholcid spiders Holocnemus pluchei (Scopoli, 1763) and Pholcus opilionoides (Schrank, 1781) are investigated with respect to functional morphology of their genital organs using freeze-fixation of spiders during copula in liquid nitrogen and subsequent preparation of histological serial sections of the copulatory organs in functional contact. Special attention is paid to the mode of male pedipalpal arrestation before copulation, which is achieved in two quite different ways: in Pholcus by contact of the lateral cheliceral apophysis with the pedipalpal trochanter-apophysis, in Holocnemus by locking the pedipalpal trochanter between chelicera and pedipalpal coxa. The condition in Pholcus is considered to be apomorphic and to present a synapomorphy of about a dozen genera for which the name “Pholcus-group” is proposed. The stridulatory apparatus of Holocnemus pluchei is described, its biological significance discussed and an overview of accounts on stridulation in Pholcidae given.