Web Construction Research Articles

Retraction Note to: Individual- and condition-dependent effects on habitat choice and choosiness

Research on consistent individual differences in behavior, or “behavioral syndromes”, continues to grow rapidly, and yet, the aspects of behavior under consideration have remained remarkably limited. Here, we consider individual variation in consistency of choice (termed here “choosiness”), as expressed during habitat choice. We repeatedly tested the responses of female Western Black Widows, Latrodectus hesperus, to two cues of habitat quality: prey chemical cues and variation in web site illuminance. We estimated females’ response by the distance they positioned themselves from (1) the source of prey chemical cues and (2) the darkest edge of our test arena. Individuals with low variance in their responses are deemed more “choosy”, whereas individuals with high variance are deemed less “choosy”. Generally, most females initiated web construction near the source of the prey chemical cues and tended to place themselves in low-light conditions. However, we detected strong, repeatable differences in females’ intensity of response, and within-individual variance of response (i.e., choosiness) was correlated across situations: females with highly consistent responses towards cricket chemical cues also exhibited highly consistent responses towards variation in light conditions. When deprived of food for extended periods, females were indistinguishable in their responses towards prey chemical cues, but tended to initiate web construction in brighter lighting conditions. Food-deprived females universally exhibited higher variance and diminished consistency in their responses (i.e., they were less choosy). Additionally, higher choosiness was associated with greater mass loss during choice trials, suggesting choosiness is energetically costly. Our results demonstrate that consistency of response to environmental cues is yet another element of behavior that varies among individuals and variation in choosiness could beget speed/quality trade-offs during animal decision making.

Studies on the Geometrical Design of Spider Webs for Reinforced Composite Structures

Spider silk is an astonishingly tough biomaterial that consists almost entirely of large proteins. Studying the secrets behind the high strength nature of spider webs is very challenging due to their miniature size. In spite of their complex nature, researchers have always been inspired to mimic Nature for developing new products or enhancing the performance of existing technologies. Accordingly, the spider web can be taken as a model for optimal fiber orientation for composite materials to be used in critical structural applications. In this study an attempt is made to analyze the geometrical characteristics of the web construction building units such as spirals and radials. As a measurement tool, we have used a developed MATLAB algorithm code for measuring the node to node of rings and radials angle of orientation. Spider web image samples were collected randomly from an ecological niche with black background sample collection tools. The study shows that the radial angle of orientation is 12.7 degrees with 5 mm distance for the spirals’ mesh size. The extracted geometrical numeric values from the spider web show moderately skewed statistical data. The study sheds light on spider web utilization to develop an optimized fiber orientation reinforced composite structure for constructing, for instance, shell structures, pressure vessels and fuselage cones for the aviation industry.

Higher-form symmetries of 6d and 5d theories

We describe general methods for determining higher-form symmetry groups of known 5d and 6d superconformal field theories (SCFTs), and 6d little string theories (LSTs). The 6d theories can be described as supersymmetric gauge theories in 6d which include both ordinary non-abelian 1-form gauge fields and also abelian 2-form gauge fields. Similarly, the 5d theories can also be often described as supersymmetric non-abelian gauge theories in 5d. Naively, the 1-form symmetry of these 6d and 5d theories is captured by those elements of the center of ordinary gauge group which leave the matter content of the gauge theory invariant. However, an interesting subtlety is presented by the fact that some massive BPS excitations, which includes the BPS instantons, are charged under the center of the gauge group, thus resulting in a further reduction of the 1-form symmetry. We use the geometric construction of these theories in M/F-theory to determine the charges of these BPS excitations under the center. We also provide an independent algorithm for the determination of 1-form symmetry for 5d theories that admit a generalized toric construction (i.e. a 5-brane web construction). The 2-form symmetry group of 6d theories, on the other hand, is captured by those elements of the center of the abelian 2-form gauge group that leave all the massive BPS string excitations invariant, which is much more straightforward to compute as it is encoded in the Green-Schwarz coupling associated to the 6d theory.

Thermal preferences of two spider species: an orb-web weaver and a synanthropic funnel-web weaver

Temperature, an important factor in the ecological niche, determines the individual fitness, distribution and abundance of many spider species. Typically, spiders from different habitats have different thermal preferences, which vary depending on the season, time of day, and reproductive status. Selected temperatures may also depend on thermal acclimation of animals. The study aimed at determining preferred temperatures of females of two spider species, synanthropic Eratigena atrica and garden Araneus diadematus, exposed to low (14°C) and high (23°C) acclimation temperatures. The mean preferred temperature observed in a thermal gradient varied between the species: E. atrica selected 13.7 ± 1.0°C, while A. diadematus selected 22.5 ± 1.5°C, irrespective of the acclimation temperature. Accordingly, thermal niche overlaps between the species were significantly lower than predicted by the random distribution. E. atrica changed their thermal environment on average 12.8 ± 1.9 times during the test, which made them more mobile than A. diadematus, changing their thermal environment 2.7 ± 0.5 times. On the other hand, the thermal niche breadth of A. diadematus acclimated to warm temperature was wider than that of E. atrica. The female behaviour may be related to the selection of optimal conditions with regard to food availability (location for web construction), shelter and/or, in the case of E. atrica, embryonic development.

Forcibly spun dragline silk fibers from web-building spider Trichonephila clavata ensure robustness irrespective of spinning speed and humidity

Web-building spiders secrete dragline silk fibers to sustain their body and use them as frameworks during web construction. They spin dragline silk fibers at various spinning speed and humidity conditions depending on their natural habitat. Here, we investigated the effect of spinning speed and humidity on the structural and mechanical properties of dragline silk fibers from web-building spider Trichonephila clavata obtained by the forcibly spinning method. We found that the crystal and morphological structures did not rely on the spinning speed and humidity. Furthermore, the mechanical strength and extensibility of the dragline silk fibers were maintained, demonstrating that dragline silk fibers ensure robustness irrespective of the spinning speed and humidity. The results obtained in the present study are helpful not only to understand the biological basis of the silk fiber formation of spiders but also contribute to consider the spinning conditions for the process of creating synthetic silk fibers.

Hub thread removal behaviour in the orb weaver Leucauge mariana (Araneae: Tetragnathidae)

Many orb-weaving spiders break the central lines of the hub at the end of web construction. Nevertheless, very little is known of how spiders break these lines and whether this behaviour differs among taxa. Here, we describe details of how Leucauge mariana (Taczanowski, 1981) breaks the central lines of the hub. Breaking hub lines varies among individuals of a single species, and may differ between species.

Orb-weaving spiders show a correlated syndrome of morphology and web structure in the wild

AbstractExtended phenotypes are traits that exist outside the physical body of organisms. Despite their role in the lives of the organisms that express them and other organisms influenced by extended phenotypes, the consistency and covariance with morphological and behavioural traits of extended phenotypes has rarely been evaluated. We repeatedly measured an extended phenotype involved in prey acquisition (web structure) of wild orb-weaving spiders (Micrathena vigorsii), which re-build their webs daily. We related web structure to behaviours and spider body length. Web diameter and web density were repeatable among individuals, reaction to a predation threat was very marginally so, and response to a prey stimulus and web evenness were not repeatable. Larger spiders spun wider webs, had webs with increased thread spacing, and the spider possibly tended to react more slowly to a predation threat. When a spider built a relatively larger web it was also a relatively less dense and less even web. The repeatability of web construction and relationship with spider body size we found may be common features of intra-population variation in web structure in spiders. By estimating the consistency and covariances of extended phenotypes we can begin to evaluate what maintains their variation and how they might evolve.

Dynamic response of spider orb webs subject to prey impact

Orb webs are strong biological structures that are crucial for orb-weaving spiders’ survival in nature. These light weight and reusable structures not only serve for prey capture but also provide vibration signal transmission to spider. In this paper, we present a model for the spider dragline silk constitutive equation, by considering its biological micro-structure. The model is validated using experimental data. A full model of spider web with two lumped masses (spider at its web center and a prey impacting a radial line) is then developed and its dynamic response due to prey impact is investigated. The results show that the dynamic response of the web is related to the amount of silk materials used in the web construction and may be little affected by the number of radial lines. The effects of pre-stretch on the dynamic response of the web is also investigated. The results show frequency of the vibration is smaller with larger pre-stretch. This is in contrast to the frequency of linear elastic string where the frequency increases with larger pre-stretch. Considering material microstructure and developed constitutive equation, this discrepancy is attributed to the reduction of shear modulus and damage to the dragline silk when pre-stretch is applied. Furthermore, the effects of damage (missing radial line) on the dynamic response of our model web are investigated. The results show that while the prey-impacted radial line transmits the largest force to the spider for undamaged web, for damaged web, other fibers could transmit larger force. The frequency of peak force that is inserted to the spider also shifts to the lower frequencies for damaged web compared to intact web. This may provide a signaling mechanism to spider that its web is damaged and should be repaired. This paper suggests possible sensing mechanisms to spider when the web is subjected to impact or its web is damaged. These suggestions should provide an avenue of research to biologist. The results obtained in this research could lead to development of artificial webs for capturing and repulsing projectile impacting the web or development of sensors.

As políticas de salvaguarda do patrimônio cultural no Brasil de 1807 a 1891

O presente artigo analisa a construção da teia cultural, no tocante às ações protecionistas ao patrimônio cultural, que se perfez desde o Brasil Império até a República (Constituição Federal de 1891). Nesse cenário, dá-se a seguinte indagação: as demandas políticas, abrangendo as transições entre formas de governo (Monarquia Absolutista, Monarquia Constitucionalista e República) do Brasil, conduziram a gestão dos patrimônios culturais? Em caso positivo, como se deu tal influência? A justificativa para essa pesquisa decorre da necessidade de se desenvolverem estudos sobre como se deu a política de salvaguarda do patrimônio cultural no Brasil durante todo o Império e após a proclamação da República, por tratar de tema de clara escassez exploratória e diante da sua concepção como tema que goza de extrema importância para a memória coletiva, por desembocar na dinâmica cultural que se tem na atualidade. Quanto aos aspectos metodológicos, desenvolve-se o estudo descritivo-analítico, bibliográfico, puro e qualitativo.

Cooperation and conflicts during prey capture in colonies of the colonial spider Parawixia bistriata (Araneae: Araneidae)

Intraspecific aggregations and colonial structures in orb-weaver spiders can reduce the per capita amount of silk to be spun, allow the use of habitats which are unavailable for solitary species, and increase protection and foraging efficiency. However, conflicts between colony members can occur during web construction, repair, and prey capture, contributing to group dissociation under conditions of low prey availability and/or in specific stages of spider maturation. While small juveniles are benefited by the joint action of many spiders during prey immobilization, older and large individuals are able to capture all available prey by themselves. For those large individuals, interactions with neighbours may compromise the amount of available resources. In this context, we evaluated the frequency of foraging events involving cooperative hunting and conflicts between residents and intruders in very young and older juveniles of Parawixia bistriata, a colonial orb-weaver spider. We recorded foraging behaviour in natural conditions and identified the main groups of insects intercepted at the webs and captured by the spiders. We then used two prey types (Lepidoptera and Orthoptera), with distinct behaviours when intercepted, in an experiment to test the influence of prey type and mass on cooperative and aggressive interactions. Most captures occurred without the participation of other individuals, and the main prey types were small Diptera and Coleoptera. Cooperative behaviour seems to occur especially between young spiderlings, but depending on prey type and size, it also occurs in late instars. The frequency of conflicts was similar in both periods of observation (November and December), with young and older individuals in colonies. Our results indicate that prey type is an important factor determining the frequency of interactions during foraging events in colonies of P. bistriata and that large spiders usually obtain success in conflicts. We suggest that these conflicts over large items may constitute a relevant variable involved in colony dissociation before spiders’ maturation.

Spinosad application in an apple orchard affects both the abundance of the spider Araneus diadematus and its web construction behaviour.

The principles of organic production are based on the respect of ecological processes including the promotion of natural enemies to control pests. However, as a last resort, some natural pesticides can be applied such as the pesticide spinosad. This neurotoxic insecticide is now widely used even in non-organic production systems. As generalist predators, spiders, and especially orb web spiders, which prey on flying pests, are thought to be useful for biocontrol. To study the effects of spinosad on orb web spiders, we applied spinosad (Success4®) at the normal application rate (96 g ha-1) in an orchard covered by nets where Araneus diadematus was very abundant. Its abundance (number of webs), location when present on the web and web characteristics were determined one day before (D - 1) and 1, 3, 6, 10 and 14 days after the application (D + 1, D + 3, D + 6, D + 10 and D + 14). After spinosad application, at D + 1 and D + 14, the number of A. diadematus webs decreased by 28% and 47%, respectively, compared to D - 1 where we observed on average 0.2 webs m-2. This decrease is likely due to a combination of direct pesticide effects, reduced prey availability and mechanical effects of the air blast sprayer. The short-term toxicity of spinosad was assessed using behavioural markers: (i) the percentage of abnormally located spiders (i.e. neither in the centre of the web nor hidden under the apple leaves) for 30 and 50% of the webs at D + 1 and D + 3 respectively, (ii) the percentage of incomplete webs (made only of the non-sticky spiral) in 35 and 75% of the cases at D + 1 and D + 3 respectively and (iii) one web characteristic, the mean parallelism between spirals, that was significantly reduced at D + 1 compared to D - 1. The study of the other web characteristics indicated that spiders did not modify the capture area but rather significantly decreased their investment in silk at D + 6 and D + 10 by reducing the number of radii and spiral turns. Overall, the application of spinosad (Success4®), representing a triple disturbance (mechanical, toxicological and alimentary), has a negative impact on the orb web spider A. diadematus and should thus be used with caution if growers want to promote the contribution of these spiders to natural biocontrol in their fields.

Keyphrase Generation With CopyNet and Semantic Web

Keyphrases provide core information for users to understand the document. Most previous works utilize machine learning based methods for keyphrases extraction and achieve promising performance. However, these methods focus on identify keyphrases from the input text, and can not extract keyphrases that do not appear in the text. In this paper, we present an encoder-decoder framework, which incorporating copying mechanism, to generate keyphrases for the given text. This framework (CopyNet) integrates the generation part and copying part. The generation part generates the keyphrase from the predefined vocabulary, and the copy part gets the keyphrases from the source text. Furthermore, we improve the CopyNet by using different probability of the two parts. To incorporate more related information for keyphrase generation, the automatically built keyphrase semantic web is merged into the dataset to participate in the training process of the neural network. Semantic similarity based and word co-occurrence based methods are used for keyphrase semantic web construction. We build a large-scale biomedical keyphrase dataset to evaluate the system performance. Experiments show that our improved CopyNet can achieve better performance with different portions of the generation and copying part, and the incorporation of the semantic web also effectively improves the keyphrase generation.

Properties of orb weaving spider glycoprotein glue change during Argiope trifasciata web construction

An orb web’s prey capture thread relies on its glue droplets to retain insects until a spider can subdue them. Each droplet’s viscoelastic glycoprotein adhesive core extends to dissipate the forces of prey struggle as it transfers force to stiffer, support line flagelliform fibers. In large orb webs, switchback capture thread turns are placed at the bottom of the web before a continuous capture spiral progresses from the web’s periphery to its interior. To determine if the properties of capture thread droplets change during web spinning, we characterized droplet and glycoprotein volumes and material properties from the bottom, top, middle, and inner regions of webs. Both droplet and glycoprotein volume decreased during web construction, but there was a progressive increase in the glycoprotein’s Young’s modulus and toughness. Increases in the percentage of droplet aqueous material indicated that these increases in material properties are not due to reduced glycoprotein viscosity resulting from lower droplet hygroscopicity. Instead, they may result from changes in aqueous layer compounds that condition the glycoprotein. A 6-fold difference in glycoprotein toughness and a 70-fold difference in Young’s modulus across a web documents the phenotypic plasticity of this natural adhesive and its potential to inspire new materials.

A spider that decorates its web perpendicular to the web plane

This paper examines and describes web decorating behavior by juveniles of the orb-weaving spider, Trichonephila antipodiana. Decorations consist of a three-dimensional ‘tube’ of silk line scaffolding within which detritus, prey items and moult exuviae are laid perpendicular to the web plane, extending from the central sticky web forward and backward to the dorsal and ventral barrier webs. Complementarity with barrier web construction, combined with the vulnerability of this ontogenetic stage, suggest that the primary function of the decorations is as an anti-predator device. Various lines of evidence support the view that the fundamental structural purpose of the decorations is perpendicular extension: (1) median web residency time was significantly greater for juveniles with decorations ≥ 1 cm in size; (2) detritus was the primary contributor to decoration length; and (3) examination of the in-laying technique for prey inclusions found them to be ‘unnecessarily’ dismembered and stretched out along the decorative plane. Although there is probably some degree of interdependence between predator avoidance and prey catching success, extension as a property fits most consistently within a defensive interpretation of function in so far as it confers either distance from and/or interference with predators.

Recombinant Pyriform Silk Fiber Mechanics Are Modulated by Wet-Spinning Conditions

Pyriform silk is a critically important fiber in spider web construction. It functions in a glue-coated attachment disc to form junctions in spider webs, connecting the web to disparate materials. Despite the biological importance of this silk, both natural and recombinant pyriform silk have yet to be structurally or mechanically characterized. In this study, we demonstrate recombinant production of a 477 amino acid protein based on Argiope argentata pyriform silk. This pyriform silk protein shows α-helicity in both an aqueous buffer and in a fluorinated acid- and alcohol-based spinning dope. Wet-spinning produced fibers having no visible defects in surface or cross-sectional analysis, with mechanical behavior varying as a function of postspin stretching conditions and correlating to loss of α-helicity in the fibrous state. Multiple conditions gave rise to fibers that are both strong and extensible, contrasting with some other silks that are biased toward being strong or extensible. This behavior is strikingly similar to recombinant aciniform silk, despite distinct primary structuring and composition.

Web construction of ABCDEFG and affine quiver gauge theories

The topological vertex formalism for 5d mathcal{N} = 1 gauge theories is not only a convenient tool to compute the instanton partition function of these theories, but it is also accompanied by a nice algebraic structure that reveals various kinds of nice properties such as dualities and integrability of the underlying theories. The usual refined topological vertex ormalism is derived for gauge theories with A-type quiver structure (and A-type gauge groups). In this article, we propose a construction with a web of vertex operators for all ABCDEF G-type and affine quivers by introducing several new vertices into the formalism, based on the reproducing of known instanton partition functions and qq-characters for these theories.

Adaptive flexibility in cues guiding spider web construction and its possible implications for spider cognition

Abstract Orb web construction was originally thought to be highly stereotyped, but adaptive flexibility is now well established in several aspects. This study reviews published data on one behavioural cue and presents new data on flexibility in experimentally modified and control webs of Zosis geniculata and Uloborus diversus. By occasionally ignoring this cue temporarily, spiders gained access to otherwise inaccessible portions of their webs. I discuss three hypotheses concerning the mechanism that resulted in this flexibility. Several types of evidence argue against the hypothesis that the adjustments were pre-programmed: substantial variation in the contexts when adjustments occurred; substantial variation in details of the adjustments; and rarity of the contexts that require adjustments in nature. Lack of plausible links between behavioural decisions and payoffs from prey capture argue against a second, learning hypothesis. By elimination, this flexibility may require a third type of explanation that includes more elaborate cognitive processes.

Dealing with Semantic Heterogeneity Issues on the Web

The Semantic Web is an extension of the traditional Web in which meaning of information is well defined, thus allowing a better interaction between people and computers. To accomplish its goals, mechanisms are required to make explicit the semantics of Web resources, to be automatically processed by software agents (this semantics being described by means of online ontologies). Nevertheless, issues arise caused by the semantic heterogeneity that naturally happens on the Web, namely redundancy and ambiguity. For tackling these issues, we present an approach to discover and represent, in a non-redundant way, the intended meaning of words in Web applications, while taking into account the (often unstructured) context in which they appear. To that end, we have developed novel ontology matching, clustering, and disambiguation techniques. Our work is intended to help bridge the gap between syntax and semantics for the Semantic Web construction.

Web spider abundance is affected by sheep farming in the Karoo

Impacts of livestock farming include effects on arthropods and a range of related ecological processes. Grazing by sheep may indirectly affect web spider populations by changing vegetation structures available for web construction, or directly by trampling the spiders or their webs. We tested these two potential impacts by surveying spiders along transects and found that web spider abundance was 52% lower in a sheep grazing area compared with inside the adjacent Tierberg-LTER (Long Term Ecological Research) sheep exclosure. This reduction in web-spider abundance could be due to the 10% lower shrub cover in the sheep pasture than in the exclosure. Further support for the hypothesis that web spider abundance is affected by shrub cover came from spider abundance being higher on densely vegetated mounds, termed heuweltjies, than in the surrounding shrub matrix in both the exclosure and the sheep pasture, with heuweltjies showing cross-fence differences, consistent with grazing impacts. In addition, there may be a direct effect of trampling, as suggested by experimental removal of webs. By depressing spider populations, sheep grazing may affect a number of ecological factors, such as trophic relationships or nutrient cycling.

The robustness, link-species relationship and network properties of model food webs

New results are collected using the Webworld model which simulates evolutionary food web construction with population dynamics (Drossel et al., 2001 [1]). We show that it supports a link-species relationship of neither constant link-density nor constant connectance, and new properties for the food webs are calculated including clustering coefficients and stability in the sense of community robustness to species deletion. Time-series for more than 40 properties of the taxonomic and trophic webs are determined over the course of individual simulations. Robustness is found to be positively correlated with connectance, but negatively with diversity, and we study the long-term development of model webs including the distribution of extinction events in a simulation with 108 speciation events.