Spider Research Articles

Two new species in the orb-weaving spider genus Larinia Simon, 1874 (Araneae, Araneidae) from Western Australia.

Two new species in the orb-weaving spider genus Larinia Simon, 1874 are described, L. sexta n. sp. and L. tumulus n. sp. This elevates the Australian number of described species in the genus to seven. With the exception of two females of L. sexta n. sp. recorded from mainland Western Australia, both species have so far exclusively been found on Barrow Island, 50 km off the north-western Western Australian coast where a third species, L. montagui Hogg, 1914, also occurs. Both new species appear to favour spinifex (Triodia spp.) grassland, but specimen numbers in collections are too low to accurately characterize life history patterns and habitat preferences.

Conspicuous cruciform silk decorations deflect avian predator attacks.

Although camouflage as an effective antipredator defense strategy is widespread across animals, highly conspicuous color patterning is not uncommon either. Many orb-web spiders adorn their webs with extra bright white silk. These conspicuous decorations are hypothesized to deter predators by warning the presence of sticky webs, camouflaging spiders, acting as a decoy, or intimidating predators by their apparent size. The decorations may also deflect predator attacks from spiders. However, empirical evidence for this deflection function remains limited. Here, we tested this hypothesis using the X-shaped silk cruciform decorations built by females of Argiope minuta. We employed visual modeling to quantify the conspicuousness of spiders and decorations from a perspective of avian predators. Then, we determined actual predation risk on spiders using naïve chicks as predators. Spider bodies and decorations were conspicuous against natural backgrounds to the avian visual systems. Chicks attacked the spider main bodies significantly less frequently on the decorated webs than on the undecorated webs, thus reducing predation risk. When both spiders and decorations were present, chicks also attacked the spider main bodies and their legs or decorations, and not randomly: they attacked the legs or decorations sooner and more frequently than they attacked the main bodies, independent of the ratio of the surface area between the decoration and spider size. Despite the increase in detectability, incorporating a conspicuous cruciform decoration to the web effectively defends the spider by diverting the attack toward the decoration or leg, but not by camouflaging or intimidating, thus, supporting the deflection hypothesis.

Taxonomy and systematics of the new Australo-Pacific orb-weaving spider genus Socca (Araneae: Araneidae)

ABSTRACT The new Australo-Pacific orb-weaving spider genus Socca is established to include 12 species from Australia: Socca pustulosa (Walckenaer, 1841) comb. nov. (type species; also present in New Zealand); S. arena sp. nov., S. australis sp. nov. S. caiguna sp. nov., S. elvispresleyi sp. nov., S. eugeni sp. nov., S. johnnywarreni sp. nov., S. kullmanni sp. nov., S. levyashini sp. nov., S. pleia sp. nov., S. senicaudata (Simon, 1908) comb. nov. (= Araneus senicaudatus simplex Simon, 1908 syn. nov.) and S. sydneyica (Keyserling, 1887) comb. nov. (= Epeira inquieta Keyserling, 1887 syn. nov.). Socca gen. nov. includes medium-sised, nocturnal orb-weaving spiders. It differs from other backobourkiine genera by five tubercles posteriorly on the abdomen and a tri-partite terminal apophysis of the male pedipalp. The epigyne plate in females is about as wide as long and the scape elongate and reaches posteriorly beyond the epigyne plate. Specimens of five Socca gen. nov. species were sequenced for the mitochondrial gene cytochrome c oxidase subunit 1 (COI). The preliminary phylogeny supports our morphological species but does not confirm species-groups based on morphology and suggests that New Zealand S. pustulosa comb. nov. populations originate from south-eastern Australia. Zoobank LSID: urn:lsid:zoobank.org:pub:FA8B2BB0-B797-4122-B4C1-1EF14B999BF2

Limitations of sperm transfer in the complex reproductive system of spiders

Abstract In spiders, sperm transfer from the male to the female is indirect via secondary copulatory structures, the pedipalps. At the time of transfer the sperm are not mobile and the ejaculate needs to move through narrow male and female ducts to the female sperm storage organ. In addition, copulation duration can be very short, often limited to just a few seconds. Finally, sexual cannibalism and genital damage limits male life-time mating opportunities. These features of the reproductive biology in spiders are likely to result in sperm transfer constraints. Here we review the intrinsic and extrinsic sperm transfer limitations and conduct a meta-analysis on sperm transfer data from published data. Most of the information available relates to orb-web spiders, but our meta-analysis also includes non-orb-web spiders. Our review identifies some of the behavioural factors that have been shown to influence sperm transfer, and lists several morphological and physiological traits where we do not yet know how they might affect sperm transfer.

Prey Impact Localization Enabled by Material and Structural Interaction in Spider Orb Webs

AbstractSpider webs are mechanical systems able to deliver an outstanding compromise between distinct requirements such as absorbing impacts and transmitting information about vibration sources. Both the frequency information and amplitude of input signals can be used by the spider to identify stimuli, aided by the mechanical filtering properties of orb webs. In this work, a numerical model based on nonlinear stress–strain constitutive relations for spider silk is introduced to investigate how the spider orb web allows spiders to detect and localize prey impacts. The obtained results indicate how the orb web center relative transverse displacements, produced by local resonance mechanisms, are used for precise localization, while nonlinear stress stiffening effects improve prey sensing. Finally, it is also shown that, although beneficial, a large number of radial threads may not be necessary for prey localization.

Strategic pheromone signalling by mate searching females of the sexually cannibalistic spider Argiope bruennichi.

Reproduction often requires finding a mating partner. To this end, females of many arthropods advertise their presence to searching males via volatile chemical signals. Such pheromones are considered low-cost signals, although this notion is based on little evidence and has recently been challenged. Even when using comparatively low-cost signals, females should signal as little as possible to minimize costs while still ensuring mate attraction. Here, we test the strategic-signalling hypothesis using Argiope bruennichi. In this orb-weaving spider, egg maturation commences with adult moult, and females that do not attract a male in time will lay a large batch of unfertilized eggs approximately three weeks after maturation. Using GC-MS analyses, we show that virgin females enhance their signalling effort, i.e. pheromone quantity per unit body mass, with increasing age and approaching oviposition. We further demonstrate that pheromone release is condition dependent, suggesting the occurrence of physiological costs. Mate choice assays revealed that pheromone quantity is the only predictor of female attractiveness for males. In support of the strategic-signalling hypothesis, pheromone signals by female A. bruennichi become stronger with increased need as well as body condition, and might thus qualify as an honest signal of female quality.

Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia

Abstract. Lia M, Rauf A, Hindayana D. 2021. Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia. Biodiversitas 23: 244-255. Vegetation structures are known to influence the microclimate and consequently the invertebrate assemblages. This study, therefore, aims to compare the species composition of assemblages of ground- and foliage-dwelling spiders in three vegetation habitats: undisturbed urban forest, oil palm plantation, and cornfield, in Bogor, West Java. To ensure a thorough representation of all spider guilds, spiders were collected using pitfall traps, sweep net, and through a direct search on ground and vegetation from January to July 2016. A total of 2299 individual spiders, representing 28 families and 207 species/morphospecies were collected. The spider species richness, abundance, and diversity were higher in the forest and oil palm plantation, compared to the cornfield. Furthermore, the dominant guild in the forest habitat was orb weavers, while the oil palm and corn habitats were dominated by ground runners. The non-metric multidimensional scaling exhibited that the composition of spider assemblages varied among the three vegetation habitats, with spider assemblages in forest habitat associated with higher RH, while the corn habitat was correlated with high light intensity and air temperature. The indicator species analysis revealed that Tetragnathidae has high potential as indicators of the dense, complex vegetation structure of the forest, while Lycosidae is indicators of the more open vegetation of oil palm plantation and cornfield habitats.

The arachnids of Glasgow Botanic Gardens

This paper provides an overview of arachnids recorded between 2017 and 2019 in Glasgow Botanic Gardens, Scotland. Species belonging to the orders Araneae (spiders), Opiliones (harvestmen), and Pseudoscorpiones (false scorpions) are included. Notable species are discussed and a comparison is made with prior information on the arachnids of the Gardens.

The novel aciniform silk protein (AcSp2-v2) reveals the unique repetitive domain with high acid and thermal stability and self-assembly capability

Orb-weaving spiders spin a mechanically and functionally diverse range of silk fibers, each composed of one or more specific silk proteins. Of all silk types, wrapping silk combines high strength and extensibility and is made of multiple aciniform silk proteins (AcSp) that can be grouped into two AcSp types (AcSp1 and AcSp2) according to their distinct repetitive regions. Here, we present a novel and complete AcSp gene from orb weaving spider Araneus ventricosus. Phylogenetic analysis of the terminal regions of spidroins reveals that the new silk protein and the published A. ventricosus AcSp2 together form a subclade, indicating that this protein is a member of AcSp2 subclass and therefore named AcSp2 variant 2 (AcSp2-v2). The repetitive region of A. ventricosus AcSp2-v2 contains 24 cysteine residues, which is the first time that cysteine has been found in repetitive regions of spidroins. Moreover, the discovery of the ability of AcSp2-v2 repetitive domain to self-assemble into silk fibers expands the repertoire of known self-assembling sequences.

Spatiotemporal dynamics of animal contests arise from effective forces between contestants

Competition among animals for resources, notably food, territories, and mates, is ubiquitous at all scales of life. This competition is often resolved through contests among individuals, which are commonly understood according to their outcomes and in particular, how these outcomes depend on decision-making by the contestants. Because they are restricted to end-point predictions, these approaches cannot predict real-time or real-space dynamics of animal contest behavior. This limitation can be overcome by studying systems that feature typical contest behavior while being simple enough to track and model. Here, we propose to use such systems to construct a theoretical framework that describes real-time movements and behaviors of animal contestants. We study the spatiotemporal dynamics of contests in an orb-weaving spider, in which all the common elements of animal contests play out. The confined arena of the web, on which interactions are dominated by vibratory cues in a two-dimensional space, simplifies the analysis of interagent interactions. We ask whether these seemingly complex decision-makers can be modeled as interacting active particles responding only to effective forces of attraction and repulsion due to their interactions. By analyzing the emergent dynamics of "contestant particles," we provide mechanistic explanations for real-time dynamical aspects of animal contests, thereby explaining competitive advantages of larger competitors and demonstrating that complex decision-making need not be invoked in animal contests to achieve adaptive outcomes. Our results demonstrate that physics-based classification and modeling, in terms of effective rules of interaction, provide a powerful framework for understanding animal contest behaviors.

Prey–predator interactions and body size relationships between annual cicadas and spiders in Japan

ABSTRACT Cicada (Hemiptera) emergence is a major resource pulse that produces diverse effects on terrestrial food webs. Most studies have focused on periodical cicadas; however, little is known regarding the prey–predator interactions and size relationships between annual cicadas and predators, with knowledge being exclusively limited to the cicada–bird systems. Here, we focused on the interactions between annual cicadas and spiders in Japan. Based on direct observations and posts on social networking services and blogs on the Internet, we aimed to (1) reveal the major spider taxa as the predators of annual cicadas, (2) identify the major cicada taxa as the prey of spiders, and (3) characterise the prey–predator body size relationships between annual cicadas and spiders. Large orb-web spiders of the family Araneidae were identified as the major predators of annual cicadas. Spiders preyed on diverse cicada species, and prey species composition varied among the predator species. Regarding body size ratio, spiders tended to prey on cicadas larger than themselves (prey–predator body size ratio >1). We suggest that orb-weavers may function as one of the key predators of annual cicadas. Annual and periodical cicadas may be preyed upon by predators that use different foraging modes (web-builders or cursorial hunters). Further examination of these prey–predator interactions will contribute to the understanding of the cicada–predator systems.

The habitat preferences of Meta bourneti (Simon, 1922) (Araneae: Tetragnathidae) in the UK differ from populations in southern Europe

Invasive species often expand their niche and broaden their habitat preferences when they colonize new areas. The cave orb spider Meta bourneti (Simon, 1922) is thought to be a relatively recent invasive species in the UK, and anecdotal evidence suggests that it might be found in a broader range of habitats in the UK than in its native range in southern Europe. In the present study, I investigate these claims, by first comparing the distribution and habitat preferences of M. bourneti to the more common cave orb spider Meta menardi (Latreille, 1804) in the UK using historic data from the UK Spider Recording Scheme. Second, I use data obtained mainly from published studies to compare M. bourneti populations in the UK with those from France, Italy, and Spain. The results confirm that the M. bourneti habitat preferences are significantly different from both M. menardi and from populations in southern Europe in that the UK populations are predominantly found in non-cave dark habitats such as under manhole covers, in culverts, and icehouses with only 11% of records coming from caves and mines. My results indicate that M. bourneti offers significant potential for further studies including citizen science projects since several observations were made in private gardens.

Take a deep breath\u2026 The evolution of the respiratory system of symphytognathoid spiders (Araneae, Araneoidea)

Spiders are unique in having a dual respiratory system with book lungs and tracheae, and most araneomorph spiders breathe simultaneously via book lungs and tracheae, or tracheae alone. The respiratory organs of spiders are diverse but relatively conserved within families. The small araneoid spiders of the symphytognathoid clade exhibit a remarkably high diversity of respiratory organs and arrangements, unparalleled by any other group of ecribellate orb weavers. In the present study, we explore and review the diversity of symphytognathoid respiratory organs. Using a phylogenetic comparative approach, we reconstruct the evolution of the respiratory system of symphytognathoids based on the most comprehensive phylogenetic frameworks to date. There are no less than 22 different respiratory system configurations in symphytognathoids. The phylogenetic reconstructions suggest that the anterior tracheal system evolved from fully developed book lungs and, conversely, reduced book lungs have originated independently at least twice from its homologous tracheal conformation. Our hypothesis suggests that structurally similar book lungs might have originated through different processes of tracheal transformation in different families. In symphytognathoids, the posterior tracheal system has either evolved into a highly branched and complex system or it is completely lost. No evident morphological or behavioral features satisfactorily explains the exceptional variation of the symphytognathoid respiratory organs.

Pemantauan Keanekaragaman Hama dan Musuh Alami Tanaman Ubi Jalar dengan Pitfall Trap

The abundance of pest and natural enemy populations on a land can be given in the diversity and abundance of feeding sources and other available resources. The purpose of this study was to determine the diversity of pests and natural enemies of sweet potato plants. Research on land with three types of sweet potatoes, namely yellow sweet potatoes with narrow leaves, yellow sweet potatoes with broad leaves, and sweet potatoes with white leaves. Around the research area are long beans, papaya, guava, soursop, and durian. Sampling of pests and natural enemies by using a pitfall trap. The data analyzed was in the form of the Shannon-Weaver (H') diversity index. The index of pest diversity of the order Coleoptera on narrow-leaved yellow sweet potato, broad-leaved yellow sweet potato, and white sweet potato was 0,160; 0,1270; and 0,1300. The index of pest diversity of the order Orthoptera on narrow-leaved yellow sweet potato, broad-leaved yellow sweet potato, and white sweet potato was 0,3585; 0,3599; and 0,3632. The index of pest diversity of the order Hemiptera on narrow-leaved yellow sweet potato, broad-leaved yellow sweet potato, and white sweet potato was 0,0635; 0,0771; and 0,1300. Diversity index of natural enemies of the order Araneae on narrow-leaved yellow sweet potato, broad-leaved yellow sweet potato, and white sweet potato 0.2180; 0.3061; and 0.2705. The three sweet potato fields had a low diversity index.

Taxonomic revision of the new spider genus Hortophora, the Australasian Garden Orb-weavers (Araneae, Araneidae)

The new genus Hortophora in the orb-weaving spider family Araneidae Clerck, 1757 is established to include 13 species from the Australasian-Pacific region, with ten species known from Australia (five of which new to science): Hortophora biapicata (L. Koch, 1871), comb. nov. (type species) (= Araneus biapicatifera Strand, 1907, syn. nov.; = Epeira frosti Hogg, 1896, syn. nov.); H. cucullussp. nov.; H. lodicula (Keyserling, 1887), comb. nov. (= Epeira scutigerens Hogg, 1900, syn. nov.); H. megacanthasp. nov.; H. porongurupsp. nov.; H. tatianeaesp. nov.; H. transmarina (Keyserling, 1865), comb. nov.) (also known from Papua New Guinea); H. urbana (Keyserling, 1887), comb. nov.; H. walesiana (Karsch, 1878), comb. nov. (= Epeira rhombocephalaThorell 1881, syn. nov.; = Epeira lutulenta Keyserling, 1886, syn. nov.); and H. yesabahsp. nov. The following species of Hortophoragen. nov. are recognised from the Pacific region but not revised in detail due to a lack of material, specifically mature males: Hortophora capitalis (L. Koch, 1871), comb. nov. (removed from synonymy with H. transmarinacomb. nov.) from Fiji, New Caledonia and Vanuatu; H. flavicoma (Simon, 1880), comb. nov. from New Caledonia (incl. Loyalty Islands) and H. viridis (Keyserling, 1865), comb. nov. (removed from synonymy with H. transmarinacomb. nov.) from Samoa. Epeira thyridota Thorell, 1870 is here removed from synonymy with H. transmarinacomb. nov. and transferred to Backobourkia Framenau, Dupérré, Blackledge & Vink, 2010, B. thyridota (Thorell, 1870), comb. nov.Hortophoragen. nov. includes medium-sized to large, nocturnal orb-weaving spiders typically with subtriangular to ovoid abdomen bearing humeral humps. The tibiae of the second leg in males is usually enlarged with numerous strong spines and an apico-ventral megaspur carrying a large spine in some species. Male pedipalps generally have an elongated, transverse median apophysis ending in a bifid tip in most species, a sinuous to straight embolus and a bubble-shaped terminal apophysis. The female epigyne scape is highly elongated and does not have a terminal pocket. Genital mutilation, i.e. breaking off the epigyne scape during copulation, is common in some species. Hortophoragen. nov. include the most frequently collected nocturnal orb-weaving spiders in Australia.

Shaped by the Sun: the effect of exposure to sunlight on the evolution of spider bodies.

Body temperature can strongly influence fitness. Some Sun-exposed ectotherms thermoregulate by adjusting body posture according to the Sun's position. In these species, body elongation should reduce the risk of heat stress by allowing the exposure of a smaller body area to sunlight. Therefore, selection should favour more elongated bodies in Sun-exposed than in Sun-protected species. Diurnal orb-web spider species that sit on their webs are more likely to be Sun-exposed, on average, than nocturnal or diurnal shelter-building species. We measured the body elongation of orb-web spiders (Araneae, Araneidae) across 1024 species and classified them as Sun-protected or exposed based on the literature. We found that Sun-exposed species evolved more elongate bodies than Sun-protected ones. Further, we built a model combining traditional heat transfer models with models of thermoregulatory postures in orb-web spiders and meteorological data. The model indicates that body elongation in large orb-web spiders decreases the risk of high body temperatures. Overall, our results suggest that Sun exposure influenced the evolution of body shapes of orb-web spiders.

Orb weavers: Patterns in the movement sequences of spider web construction

Quantitative behavior analyses of spider movements- large and small- reveal repeated action sequences that define stages of web building.

Influence of web traits, height, and daily periods of exposition on prey captured by orb-weaver spiders

Orb-webs show diversity in several traits, including silk types, architecture, physical properties, locale, and period of exposition. The investigation of how they determine the identity of intercepted prey is important to functional ecology and to the evaluation of trophic niche partitioning within communities. However, the influence of several of these variables on the composition of intercepted insects remains to be determined. In this study, we evaluated the effects of web architectural traits, height, and daily periods of exposition on the interception of different insects in terms of sizes, masses, and taxa. We conducted observations of prey intercepted by the orb webs of 16 sympatric spider species and artificial webs. We found that all orb webs mainly intercepted small and light insects, sharing the most abundant insect families found in the study area. However, spiders that show nocturnal activity, more radii in their webs, large and high webs captured heavier insects. Other orb-web traits, such as the density of capture threads did not influence the kind of intercepted insects. We discuss why some variables affected prey interceptions in terms of mass. Finally, we discuss the implications of these influential variables to functional ecology, niche differentiation, and how behavioral assessments can complete this investigation in future studies.

Mate-guarding duration is mainly influenced by the risk of sperm competition and not by female quality in a golden orb-weaver spider.

Males are expected to mate with as many females as possible, but can maximize their reproductive success through strategic mating decisions. For instance, males can increase their own fitness by mating with high quality females that produce more offspring. Additionally, males can adjust mating effort based on the relative distribution of females and male competitors. To test factors that influence male mate choice, we assessed male mating decisions in the golden silk orb-weaver spider, Trichonephila clavipes (Nephilidae), a species in which females are polyandrous, males guard females before and after copulation occurs and large males are the most successful at guarding mates. We tested the hypothesis that males spend more time guarding high quality females that are spatially isolated, and when the risk of sperm competition is higher. We also hypothesized that this effect increases with male body size. We assessed solitary and aggregated female webs in the field and quantified female quality (i.e., female body condition), male size (i.e., male body size), the risk of sperm competition (i.e., number of males in each female web), and mate-guarding duration (i.e., number of days each male spent in each web). We found that mate-guarding behaviour is largely influenced by the presence of male competitors. In addition, male body size seems to moderately influence male guarding decisions, with larger males guarding for a longer time. Finally, female body condition and type of web (i.e., solitary or aggregated) seem to play small roles in mate-guarding behaviour. As mate-guarding duration increased by 0.718 day per each additional male competitor in the web, and guarding behaviour prevents males from seeking additional mates, it seems that guarding females can be considerably costly. We conclude that failing to guard a sexual partner promotes high costs derived from sperm competition, and a male cannot recover his relative loss in fertilization success by seeking and fertilizing more females. In addition, the search for more sexual partners can be constrained by possible high costs imposed by weight loss and fights against other males, which may explain why the type of web only moderately influenced male mate choice. Following the same rationale, if high-quality females are not easy to find and/or mating with a high-quality female demands much effort, males may search females and guard them regardless of female quality. In conclusion, the factor that most influences male mate-guarding behaviour among T. clavipes in the field is the risk of sperm competition.

Some Spiny Backed Orb-Weaving Spiders (Araneae: Araneidae) From Bangladesh

Spiny backed orb-weaving spiders sampled from different areas of Khulna and Bagerhat, Bangladesh were dealt with. Three species of the genus Gasteracantha Sundevall were recorded that includes one new species G. chowdhuryi n. sp. Generic diagnosis, illustrated description and distribution together with key to the species were provided herewith. J. Biodivers. Conserv. Bioresour. Manag. 2020, 6(2): 35-46