Web Building Research Articles

Allometry and ecology shape eye size evolution in spiders

Eye size affects many aspects of visual function, but eyes are costly to grow and maintain. The allometry of eyes can provide insight into this trade-off, but this has mainly been explored in species that have two eyes of equal size. By contrast, animals possessing larger visual systems can exhibit variable eye sizes within individuals. Spiders have up to four pairs of eyes whose sizes vary dramatically, but their ontogenetic, static, and evolutionary allometry has not yet been studied in a comparative context. We report variable dynamics in eye size across 1,098 individuals in 39 species and 8 families, indicating selective pressures and constraints driving the evolution of different eye pairs and lineages. Supplementing our sampling with a recently published phylogenetically comprehensive dataset, we confirmed these findings across more than 400 species; found that ecological factors such as visual hunting, web building, and circadian activity correlate with eye diameter; and identified significant allometric shifts across spider phylogeny using an unbiased approach, many of which coincide with visual hunting strategies. The modular nature of the spider visual system provides additional degrees of freedom and is apparent in the strong correlations between maximum/minimum investment and interocular variance and three key ecological factors. Our analyses suggest an antagonistic relationship between the anterior and posterior eye pairs. These findings shed light on the relationship between spider visual systems and their diverse ecologies and how spiders exploit their modular visual systems to balance selective pressures and optical and energetic constraints.

How dispersal rates depend on the prey capture strategy: A case study of Georgia's spiders.

Large-scale barcoding projects help to aggregate information on genetic variability of multiple species throughout their ranges. Comparing DNA sequences of both non-conspecific and conspecific individuals from distant parts of their ranges helps to compare level of genetic isolation-by-distance patterns in different species and adaptive types. We compared mitochondrial CO1 gene sequences of 223 spiders from Georgia (Caucasus), representing 124 species and eight families, with 3097 homological sequences from spiders mostly from Europe, but also from other parts of the World. In most families, a significant isolation-by distance pattern was observed on family level. On species level, a significant isolation-by-distance was observed in 40 species, although this low proportion is most likely related to a lack of data. Simultaneously, remarkable differences in spatial structure were shown for different species. Although the majority of the studied species have a broad western Palearctic range, web-building spiders from families Araneidae, Theridiidae, and Linyphiidae are less isolated spatially than flower spiders (Thomisidae), jumping spiders (Salticidae), wolf spiders (Lycosidae), sac spiders (Clubionidae), and ground spiders (Gnaphosidae). This pattern is related with more common ballooning in web building than in actively hunting spiders, which commonly remain isolated since preglacial time. Ground spiders build the most isolated populations in the Caucasus.

Study on structure and types of spider webs from Nagpur district Maharashtra India

The structure of spider webs varies substantially between species, and web building has even been lost completely in some clades. Examples of different web forms include the classic orb webs, which may be oriented vertically to the ground or horizontally, sheet webs, and cobwebs, consisting of three-dimensional meshwork and ascending sticky threads for support and capture of prey. The primary function of spider webs is to capture prey. This ecological success is in part due to the exceptional mechanics of the spider web, with its strength, toughness, elasticity, and robustness, which originate from its hierarchical structures from sequence design to web architecture. Hence a preliminary survey was carried out to structure and identify types of spider webs from Nagpur district, Maharashtra, India. This study explores the structure and identification of spider webs (Arachnids) in the Nagpur District of Maharashtra. Sampling was carried out in 8 months from January 2024 to August 2024 during the weak and month wise. Spider webs are collected using a Photograph collection and black paper for the collection of type’s spider webs. The results of the study concluded that a total of 8 types of spider webs were collected there were Site A 3 types of spider webs, Site B 3 types of spider webs, Site C 1 type of spider web and Site D 1 type of spider web were identified. A total 8 types of spider webs are identified, the names of types of spider webs are the total 8 types of spider webs Identified in Nagpur district the following types of spider webs are the Funnel-web of spider, Sheet web, Classic round webs of spider webs or Orb webs, Mesh web of a spider, Cobweb of spider, Tangle web, Messy web of a spider, and Triangle web of spider.

Temporal variation in spider trophic interactions is explained by the influence of weather on prey communities, web building and prey choice

Generalist invertebrate predators are sensitive to weather conditions, but the relationship between their trophic interactions and weather is poorly understood. This study investigates how weather affects the identity and frequency of spider trophic interactions over time, alongside prey community structure, web characteristics and prey choice. Spiders (Linyphiidae and Lycosidae) and their prey were collected from barley fields in Wales, UK, from April to September 2017–2018. The gut contents of 300 spiders were screened using DNA metabarcoding, analysed via multivariate models and compared against prey availability using null models. When linyphiids were collected from webs, the height and area of webs were recorded and compared against weather conditions. Trophic interactions changed over time and with weather conditions, primarily related to concomitant changes in prey communities. Spiders did, however, appear to mitigate the effects of structural changes in prey communities through changing prey preferences according to prevailing weather conditions, possibly facilitated by adaptive web construction. Using these findings, we demonstrate that prey choice data collected under different weather conditions can be used to refine inter‐annual predictions of spider trophic interactions, although prey abundance was secondary to diversity in driving the diet of these spiders. By improving our understanding of the interaction between trophic interactions and weather, we can better predict how ecological networks are likely to change over time in response to variation in weather conditions and, more urgently, global climate change.

A novel probe set for the phylogenomics and evolution of RTA spiders.

Spiders are important models for evolutionary studies of web building, sexual selection and adaptive radiation. The recent development of probes for UCE (ultra-conserved element)-based phylogenomic studies has shed light on the phylogeny and evolution of spiders. However, the two available UCE probe sets for spider phylogenomics (Spider and Arachnida probe sets) have relatively low capture efficiency within spiders, and are not optimized for the retrolateral tibial apophysis (RTA) clade, a hyperdiverse lineage that is key to understanding the evolution and diversification of spiders. In this study, we sequenced 15 genomes of species in the RTA clade, and using eight reference genomes, we developed a new UCE probe set (41 845 probes targeting 3802 loci, labelled as the RTA probe set). The performance of the RTA probes in resolving the phylogeny of the RTA clade was compared with the Spider and Arachnida probes through an in-silico test on 19 genomes. We also tested the new probe set empirically on 28 spider species of major spider lineages. The results showed that the RTA probes recovered twice and four times as many loci as the other two probe sets, and the phylogeny from the RTA UCEs provided higher support for certain relationships. This newly developed UCE probe set shows higher capture efficiency empirically and is particularly advantageous for phylogenomic and evolutionary studies of RTA clade and jumping spiders.

Captivity Induced Web Spinning of Plexippus petersi (Karsch,1878) (Jump/Zebra Spider) of Chennai, India

Plexippus petersi, common jump/zebra spider of Chennai households, belongs to the family of Salticidae. Though spinning of a web is considered to be an inbuilt feature of almost all the spiders, certain spiders do not spin typical webs, and Plexippus petersi is one of them. The present study was undertaken, to investigate if this species of spiders can build a web when exposed to any sort of calamity. In this regard, male and female spiders were carefully handpicked, identified and maintained under laboratory condition for a period of four days. After the experimental period, the spiders were relived from captivity and were individually photographed. During the experimental period, it was quite fascinating to observe that the female of this species, secreted silk threads from her abdominal glands, and were woven in to a sheet web. The silk of the web, was sticky in nature, white in color and was able to be molded in to long filamentous structure. This web spinning behavior was only observed in the female and not in male spiders. The results of this study precisely illustrate the fact that, when triggered under the pressure of a disaster, the female spiders can weave a web and evade any uncertainty This amusing observational study, gives a deeper acumen not only about the behavioral aspect, but also explains, the probable success of these tiny arachnids, in evolution which may be probably attributed to their jumping behavior and web building strategy of the females. The female spiders, seem to weave the web, not just for escape from predators, catching the prey, and protection of egg cases but also to escape from adversaries at uncertain times.

Conversations as Vessels and Anchors

Conversations as Vessels and Anchors

Population ecology of the orb-weaver spider Eustala taquara (Keyserling) (Araneidae)

ABSTRACT The density and age structure of spider populations are affected by biotic and abiotic factors. The orb-web spider Eustala taquara (Araneidae) lives camouflaged on the dead vegetation of shrubs, especially in forest edges. Here, we describe the variation in the number of individuals over the year and the phenology of a population of E. taquara. We also tested whether these variables are influenced by temperature, precipitation or prey availability. We conducted the research in a tropical rainforest located in south-eastern Brazil. We recorded the number of spiders and their development stages (spiderling, young, juvenile, sub-adult and adult) monthly, for two years, along 1 km at the forest edge at an altitude of 1000 m above sea level. We estimated prey availability using 20 circular transparent plates containing tanglefoot on one side, exposed for 48 hours in the vegetation, sampled monthly for 18 months. We used circular statistics to assess the peaks of individuals during the study period, verifying the occurrence of time lags between the number of spiders with the climatic variables and prey availability. The population of E. taquara increased in periods of lower precipitation and temperature, and decreased during the rainy season. Thus, the population showed a negative correlation with the climatic variables and potential prey availability. All instars were present simultaneously, revealing that spiders can reproduce at any time of year. During the dry season, the higher number of spiders may be related to the increase in branches and dead plants that provide camouflage against visually oriented predators and sites for web building, increasing the likelihood of obtaining food.

Web building behavior in a wall spider (Oecobiidae) suggests a close relationship with orb-weavers

Behavior is often phylogenetically informative and detailed descriptions of behavior have been used to support taxonomic relationships in several groups, such as birds, lizards, and arthropods. Web building behavior has provided informative traits to several spider families, but observations are lacking for other families, such as wall spiders Oecobiidae. Recent phylogenetic hypotheses based on molecular traits placed oecobiids either close to cribellate orb weavers (Uloboridae) or to long-spinneret spiders (Hersiliidae). Here, we describe for first time the web construction behavior and details of the web design in the oecobiid Oecobius concinnus Simon 1893 (Oecobiidae). We compare them with uloborid and araneoid orb weavers. If Oecobiidae and Uloboridae are closely related, we expect that O. concinnus share some web construction behaviors with these orb weavers. Video recordings and analyses of web structures suggest the sequence of web construction (radii, then sticky spiral construction) and the arrangement of cribellate threads are possible homologies between Oecobiidae and orb weavers, supporting a close relationship of Oecobiidae with Uloboridae.

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.

Distinct movement patterns generate stages of spider web building

The geometric complexity and stereotypy of spider webs have long generated interest in their algorithmic origin. Like other examples of animal architecture, web construction is the result of several assembly phases that are driven by distinct behavioral stages coordinated to build a successful structure. Manual observations have revealed a range of sensory cues and movement patterns used during web construction, but methods to systematically quantify the dynamics of these sensorimotor patterns are lacking. Here, we apply an analytical pipeline to quantify web-making behavior of the orb-weaver Uloborus diversus. Position tracking revealed stereotyped stages of construction that could occur in typical or atypical progressions across individuals. Using an unsupervised clustering approach, we identified general and stage-specific leg movements. A hierarchical hidden Markov model revealed that web-building stages are characterized by stereotyped sequences of actions largely shared across individuals, regardless of whether these stages progress in a typical or an atypical fashion. Web stages could be predicted based on action sequences alone, revealing that web-stage geometries are a physical manifestation of behavioral transition regimes.

Cross-Ecosystem Linkages: Transfer of Polyunsaturated Fatty Acids From Streams to Riparian Spiders via Emergent Insects

Polyunsaturated fatty acids (PUFAs) are essential resources unequally distributed throughout landscapes. Certain PUFAs, such as eicosapentaenoic acid (EPA), are common in aquatic but scarce in terrestrial ecosystems. In environments with low PUFA availability, meeting nutritional needs requires either adaptations in metabolism to PUFA-poor resources or selective foraging for PUFA-rich resources. Amphibiotic organisms that emerge from aquatic ecosystems represent important resources that can be exploited by predators in adjacent terrestrial habitats. Here, we traced PUFA transfer from streams to terrestrial ecosystems, considering benthic algae as the initial PUFA source, through emergent aquatic insects to riparian spiders. We combined carbon stable isotope and fatty acid analyses to follow food web linkages across the ecosystem boundary and investigated the influence of spider lifestyle (web building vs. ground dwelling), season, and ecosystem degradation on PUFA relations. Our data revealed that riparian spiders consumed considerable amounts of aquatic-derived resources. EPA represented on average 15 % of the total fatty acids in riparian spiders. Season had a strong influence on spider PUFA profiles, with highest EPA contents in spring. Isotope data revealed that web-building spiders contain more aquatic-derived carbon than ground dwelling spiders in spring, although both spider types had similarly high EPA levels. Comparing a natural with an anthropogenically degraded fluvial system revealed higher stearidonic acid (SDA) contents and Σω3/Σω6 ratios in spiders collected along the more natural river in spring but no difference in spider EPA content between systems. PUFA profiles of riparian spiders where distinct from other terrestrial organism and more closely resembled that of emergent aquatic insects (higher Σω3/Σω6 ratio). We show here that the extent to which riparian spiders draw on aquatic PUFA subsidies can vary seasonally and depends on the spider’s lifestyle, highlighting the complexity of aquatic-terrestrial linkages.

Friend and foe? The effects of grassland management on global patterns of spider diversity

1. Grassland ecosystems have been used worldwide for food production through pastoral and cropping activities. In these ecosystems, spiders constitute important mesopredators, which are affected by grassland management in opposite ways. Historically, the spider taxonomic diversity has been the main focus in studies of grazing impacts in grassland ecosystems, while the intrinsic variability of traits within spiders have been neglected, which may have led to mistaken conclusions. Our objective is to reanalyse the effects of grazing on spider taxonomic and functional guilds on worldwide grasslands.2. We conducted a systematic review of the literature from the last 10 years, to assess the influence of grazing on the taxonomic and functional guild diversity of spiders worldwide. Using Generalised Linear Mixed Models, we assessed the effects of grazing pressure and type of herd on abundance, richness of spider species, and guilds.3. In the taxonomic perspective, we found no evidence of grazing impact on the abundance and richness of spiders. However, in the functional guild perspective, high grazing pressure reduced the diversity of web building spiders and enhanced diversity of ground dwelling spiders. Moreover, pastures containing more than one grazing species enhanced the diversity of ambush spiders.4. Overall, the functional guild diversity of spiders in grassland ecosystems seems to be more influenced by grazing intensity. Our results suggest that grazing intensity can change the guild composition of the araneofauna in grasslands, with guilds responding differently to grazing.

Dynamic environments do not appear to constrain spider web building behaviour

Many laboratory experiments demonstrate how orb-web spiders change the architecture of their webs in response to prey, surroundings and wind loading. The overall shape of the web and a range of other web parameters are determined by frame and anchor threads. In the wild, unlike the lab, the anchor threads are attached to branches and leaves that are not stationary but move, which affects the thread tension field. Here we experimentally test the effect of a moving support structure on the construction behaviour and web-parameters of the garden cross spider Araneus diadematus. We found no significant differences in building behaviour between rigid and moving anchors in total time spent and total distance covered nor in the percentage of the total time spent and distance covered to build the three major web components: radials, auxiliary and capture spirals. Moreover, measured key parameters of web-geometry were equally unaffected. These results call for re-evaluation of common understanding of spider webs as thread tensions are often considered to be a major factor guiding the spider during construction and web-operation.

Spiders in space\u2014orb-web-related behaviour in zero gravity

Gravity is very important for many organisms, including web-building spiders. Probably the best approach to study the relevance of gravity on organisms is to bring them to the International Space Station. Here, we describe the results of such an experiment where two juvenile Trichonephila clavipes (L.) (Araneae, Nephilidae) spiders were observed over a 2-month period in zero gravity and two control spiders under otherwise identical conditions on Earth. During that time, the spiders and their webs were photographed every 5 min. Under natural conditions, Trichonephila spiders build asymmetric webs with the hub near the upper edge of the web, and they always orient themselves downwards when sitting on the hub whilst waiting for prey. As these asymmetries are considered to be linked to gravity, we expected the spiders experiencing no gravity to build symmetric webs and to show a random orientation when sitting on the hub. We found that most, but not all, webs built in zero gravity were indeed quite symmetric. Closer analysis revealed that webs built when the lights were on were more asymmetric (with the hub near the lights) than webs built when the lights were off. In addition, spiders showed a random orientation when the lights were off but faced away from the lights when they were on. We conclude that in the absence of gravity, the direction of light can serve as an orientation guide for spiders during web building and when waiting for prey on the hub.

Black widows on an urban heat island: extreme heat affects spider development and behaviour from egg to adulthood

Urbanization rapidly alters the environment, often leading to decreased biodiversity. One abiotic selection pressure uniquely associated with urbanization is the urban heat island (UHI) effect—wherein built structures (e.g. paved surfaces) capture heat during the day, retain it through the dark cycle and result in significantly elevated night-time temperatures. Relatively few studies have asked what effects the UHI might have on the development and behaviour of urban animals, and even fewer have asked this question of urban arthropod pests who rely on external heat sources and can experience explosive urban population growth rates. In particular, behavioural plasticity is often cited as a critical phenotype for organisms to thrive after rapid environmental change such as urbanization. Here, the relationship between elevated urban temperatures and behaviour was examined in the western black widow spider, Latrodectus hesperus. With regard to the UHI, young spiderlings raised at urban, elevated temperatures showed significantly reduced life span, reduced body mass, elevated web building, heightened voracity towards heterospecific prey and sibling cannibalism. In contrast, males studied later in the final prereproductive moults and raised at urban, elevated temperatures showed reduced life span, decreased adult body condition and increased voracity towards prey. We found no effects of temperature on late-stage male web building or courtship behaviour. UHI temperatures simulated in the laboratory present black widow spiders with a myriad of developmental problems, but our data suggest these spiders use temperature-sensitive behavioural plasticity to attempt to accommodate this stressor.

Ontologías: análisis de sus implementaciones en la bibliotecología

El objetivo del artículo es determinar las implementaciones que las ontologías tienen en la bibliotecología. La hipótesis inicial estableció que pueden funcionar como un sistema para la organización del conocimiento (SOC), con funciones similares a los encabezamientos de materia o los tesauros. La metodología empleada consistió en revisión bibliográfica y análisis de casos. Los resultados evidencian que las ontologías en la disciplina bibliotecología pueden implementarse en cinco funciones: 1) representación estructurada de dominios, 2) indización de recursos de información digitales, 3) generación de aprendizaje entre estudiantes y usuarios, 4) construcción de la web semántica, y 5) estructuración de redes de datos enlazados. A partir de los resultados, se confirmó que pueden ser empleadas como un SOC pero, además, pueden ser aplicadas en tareas generales para el modelado de datos o información en la web. Se concluye que son sistemas con alto potencial en la representación y organización de la información en contextos digitales.

Modeling wildfire ignition origins in southern California using linear network point processes

This paper focuses on spatial and temporal modeling of point processes on linear networks. Point processes on linear networks can simply be defined as point events occurring on or near line segment network structures embedded in a certain space. A separable modeling framework is introduced that posits separate formation and dissolution models of point processes on linear networks over time. While the model was inspired by spider web building activity in brick mortar lines, the focus is on modeling wildfire ignition origins near road networks over a span of 14 years. As most wildfires in California have human-related origins, modeling the origin locations with respect to the road network provides insight into how human, vehicular and structural densities affect ignition occurrence. Model results show that roads that traverse different types of regions such as residential, interface and wildland regions have higher ignition intensities compared to roads that only exist in each of the mentioned region types.

Physical and social cues shape nest-site preference and prey capture behavior in social spiders.

Animals often face conflicting demands when making movement decisions. To examine the decision process of social animals, we evaluated nest-site preferences of the social spider Stegodyphus dumicola. Colonies engage in collective web building, constructing 3D nests and 2D capture webs on trees and fences. We examined how individuals and groups decide where to construct a nest based on habitat structure and conspecific presence. Individuals had a strong preference for 3D substrates and conspecific presence. Groups were then provided with conflicting options of 3D substrates versus 2D substrates with a conspecific. Groups preferred the 3D structures without presettled conspecifics over a 2D substrate with conspecifics. When a group fragmented and individuals settled on both substrates, the minority group eventually joined the majority. Before rejoining, the collective prey capture behavior of divided groups improved with the size of the majority fragment. The costs of slow responses to prey for split groups and weak conspecific attraction may explain why dispersal is rare in these spiders.

A Spider's Vibration Landscape: Adaptations to Promote Vibrational Information Transfer in Orb Webs.

Spider orb webs are used not only for catching prey, but also for transmitting vibrational information to the spider. Vibrational information propagates from biological sources, such as potential prey or mates, but also abiotic sources, such as wind. Like other animals, the spider must cope with physical constraints acting on the propagation of vibrational information along surfaces and through materials-including loss of energy, distortion, and filtering. The spider mitigates these physical constraints by making its orb web from up to five different types of silks, closely controlling silk use and properties during web building. In particular, control of web geometry, silk tension, and silk stiffness allows spiders to adjust how vibrations spread throughout the web, as well as their amplitude and speed of propagation, which directly influences energy loss, distortion, and filtering. Turning to how spiders use this information, spiders use lyriform organs distributed across their eight legs as vibration sensors. Spiders can adjust coupling to the silk fibers and use posture to modify vibrational information as it moves from the web to the sensors. Spiders do not sense all vibrations equally-they are least sensitive to low frequencies (<30 Hz) and most sensitive to high frequencies (ca. 1 kHz). This sensitivity pattern cannot be explained purely by the frequency range of biological inputs. The role of physical and evolutionary constraints is discussed to explain spider vibration sensitivity and a role of vibration sensors to detect objects on the web as a form of echolocation is also discussed.