Web-building Behaviour Research Articles

Investigating the Influence of Anthropogenic Activities on Behavioral Changes of an Orb Web Spider (Neoscona vigilans).

Orb web spiders are common and highly diversified animals found in almost all habitats. They have remarkable plasticity against biotic and abiotic factors, making them excellent indicators of environmental health. The web creation behavior of spiders is influenced by disturbances in the environment. The aim of this research was to observe the alteration in the web-building behavior of Neoscona vigilans caused by human activities, specifically traffic disturbances. Spider webs were located and photographed at nighttime along the roadside, and their web characteristics were calculated. Spiders were captured from webs for their body measurements. Spider fourth leg length, carapace width, and body length had a significant association with web size and diameter, CTL, capture area, and mesh size. The quantity of trapped prey, the height of the plant, and the foliage radius increased with the distance from the road. Conversely, anchor points and web elevation from the ground dropped. The highest and lowest proportions of anomalies (modifications/defects) were recorded as holes (52.7%) in 105 webs (100%) and supernumerary (0.7%) in 55 webs (52.4%), respectively. Road disturbance had a negative influence on the spider's behavior as the webs formed in close proximity to the road had a higher frequency of anomalies, with a gradual decrease distantly. We can gain further insight into how different environmental changes, disruptions, and pollutants lead to this imperfection in the otherwise flawless perfect structure of spider webs.

A bionomic overview of spider parasitoids and pseudo-parasitoids of the ichneumonid wasp subfamily Pimplinae

Abstract The parasitoid way of life (parasitizing and finally killing a single arthropod host) is one of the most successful lifeways in the animal kingdom, sparking an explosive diversification and accompanying numerous parasitoid strategies in insects, especially in the order Hymenoptera. Amongst parasitoid wasps, the Polysphincta group of genera has evolved a highly distinctive parasitoid mode of life, as solitary koinobiont ectoparasitoids of spiders (Chelicerata: Araneae). Some species of polysphinctine wasps have a remarkable ability to control spiders’ web-building behaviour (host web manipulation) to protect the vulnerable wasp cocoons. The group currently consists of 25 genera and 294 extant species worldwide, with 14 genera known to manipulate their host spiders. This study reviews the current species composition, distribution, host utilization and biology of all genera belonging to the Polysphincta group and their ancestral genera of spider egg mass pseudo-parasitoids, highlighting specific offensive approaches for subjugating spider hosts for oviposition and web manipulation against specific spider hosts. There must still be many more unique behaviours to be discovered, given that the life histories of several polysphinctine genera are poorly known or unknown. A tidy correspondence between lineages of polysphinctines and host spiders was recognized, implying the evolutionary history of polysphinctines. Based on the integrated information on behavioural data and host utilization, we suggest some hypotheses determining triggers for host shifts and discuss the possibility of adaptive radiation driven by divergent natural selection on host differentiation. One new taxonomic change is proposed: Zaglyptus idukkiensis (Manjusha, Sudheer & Ghosh, 2019), comb. nov., is transferred from Polysphincta.

Economic web-building behavior and behavioral investment trade-offs in a cobweb spider

Web-building spiders that build detritus-based bell-shaped cobwebs are model organisms for studies on behavioral plasticity because their web architecture components are easily quantified and behavioral investments are clearly separated. We investigated the web architectures and behavioral investments of the cobwebs built by Campanicola campanulata under different weight (heavy, medium, and light) detritus to research its cobweb architecture variation and analyzed the investment trade-off between foraging and defense. The results showed that spiders could actively choose lighter detritus to build retreats to reduce material and energy cost. There was a clear trade-off between defense and foraging investment of spiders choosing different weight detritus for their webs. The total length of gumfooted lines (foraging investment) was longer for the spiders that chose lighter detritus, but the energy expenditure during web-building (defense investment) was higher for the spiders that chose heavier detritus.

Web construction behavior of Deinopis cf. cylindracea (Deinopidae: Araneae) and its comparison to webs of other Deinopidae

Deinopid spiders use highly specialized webs composed of a triangular non-sticky scaffolding (NS scaffolding) containing three radii and a modified orbicular web with a rectangular shape to capture prey. Spiders actively manipulate their webs to capture prey. We describe the web construction behavior of Deinopis cf. cylindracea and compare it and the shape of the sticky silk spiral (SS spiral) of other deinopid species using images in the literature and on the Internet. The web-building behavior in D. cf. cylindracea follows the pattern previously described for other species of Deinopis MacLeay, 1839. Web construction takes approximately 15 min in D. cf. cylindracea and has two stages: NS scaffolding construction and SS spiral construction. The final structure of the SS spiral has four closely spaced capture cords, five placed further apart, three near the top of the web, and two cords on the handles, making a total of 12. Other species of Deinopis have different numbers of cords. Finally, a novel finding is that the youngest spiders do not make webs with sticky lines, but instead use a simplified web to lunge forward, using only their legs to contact prey. To our knowledge, such behavior has never been described in this or any other group.

Two new species and a new genus of ray spiders (Araneae, Theridiosomatidae) from the Ryukyu Islands, southwest Japan, with notes on their natural history.

This paper provides descriptions of two new theridiosomatid species, Theridiosomanigrivirgatum sp. nov. and Sennintanikawai gen. nov., sp. nov. from the Ryukyu Islands, southwest Japan, with photographs and illustrations of both sexes. Sennin gen. nov. is a troglophilic genus composed of two species, S.tanikawai sp. nov. (Iriomote Island, Japan) and S.coddingtoni (Zhu, Zhang & Chen, 2001), comb. nov. (southern China). Zomadibaiyin Miller, Griswold & Yin, 2009, which recently joined the Japanese fauna, was morphologically reexamined based on specimens from the Ryukyus, and taxonomic features of Zoma males were reassessed. A distributional map of theridiosomatid spiders in the Ryukyus is also provided, including T.dissimulatum Suzuki, Serita & Hiramatsu, 2020, and T.alboannulatum Suzuki, Serita & Hiramatsu, 2020 with their habitat types, web morphology, and web-building behavior in detail.

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.

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.

Natural history of the ogre-faced spider Deinopis cf. cylindracea (Araneae: Deinopidae): revealing its phenology

ABSTRACT Deinopidae spiders are known mainly for their web-building behavior and prey-capture strategy. However, studies on their population ecology are scarce. Therefore, we evaluated the population fluctuation, phenology, and diet of Deinopis cf. cylindracea. We also investigated how abiotic (precipitation and temperature) and biotic (prey availability) factors influence the abundance of this species. Our results showed that D. cf. cylindracea has an annual cycle with a maximum density in March. The reproduction cycle occurs from March to July. The recruitment of spiders occurred between July and October, followed by a peak of young individuals in December, juveniles in February, subadults in April, and adults in May, indicating a ‘fall stenochronous’ phenological pattern. The climatic variables were important factors that influenced the fluctuation of the age of D. cf. cylindracea. Although we did not find a positive correlation between the climate and its abundance at time 0, we did observe a correlation with a delay of three months. The main preys were Formicidae and Coleoptera, and not all available preys were part of the spiders’ diet. These results indicate that the spiders require time to respond to changes in environmental conditions and provide information about the different stages of development over time.

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.

Orb-weaving spiders are fewer but larger and catch more prey in lit bridge panels from a natural artificial light experiment.

Artificial light at night is rapidly changing the sensory world. While evidence is accumulating for how insects are affected, it is not clear how this impacts higher trophic levels that feed on insect communities. Spiders are important insect predators that have recently been shown to have increased abundance in urban areas, but have shown mixed responses to artificial light. On a single bridge with alternating artificially lit and unlit sections, I measured changes in the orb-weaving spider Larinioides sclopetarius (Araneidae) web abundance, web-building behavior, prey-capture, and body condition. In artificially lit conditions, spiders caught more prey with smaller webs, and had higher body conditions. However, there were fewer spiders with active webs in those lit areas. This suggests that either spiders were not taking advantage of an ecological insect trap, perhaps due to an increased risk of becoming prey themselves, or were satiated, and thus not as active within these habitats. The results from this natural experiment may have important consequences for both insects and spiders in urban areas under artificial lighting conditions.

Web-building behavior of the odd-clawed spider Progradungula otwayensis (Araneae: Gradungulidae) and implications for the evolution of combing behavior in spiders

This study explores the web-building behavior of Gradungulidae for the first time, using the Otway odd-clawed spider Progradungula otwayensisMilledge, 1997. The web consists of a signal line leading to a retreat, an upper scaffold and a cribellate catching ladder connected to the substrate. The construction sequence and final structure of the catching ladder are highly stereotyped, especially in the initial segments of the cribellate capture thread. Two vertical rail lines—made of thin cribellate silk that is not combed with the calamistrum—are connected by looping segments of combed, much thicker cribellate capture threads. Small juveniles make a relatively larger non-sticky supporting scaffold with some cribellate silk on it. Microscopic analysis of the silk revealed that the cribellate bands have a pair of axial lines and a pair of reserve warps; the cribellate fibrils have nodules. The non-sticky structural lines are made of straight or coiling lines, changing gradually from straight to coiling; each of these structural lines is composed of tightly appressed fibrils, probably associated with the occurrence of multiple ampullate gland spigots. During combing behavior both legs IV are used synchronously. The same combing behavior is performed by the Tasmanian cave spider Hickmania troglodytes (Higgins & Petterd, 1883). We conclude that both type I and type II combing behaviors are monophyletic, although it is unclear which one is ancestral. Given the phylogenetic position of ProgradungulaForster & Gray, 1979, we suggest that the ability to measure with precision and produce repetitive, stereotyped silk structures made of specific silk types may have arisen close to the ancestor of araneomorph spiders.

A preliminary molecular phylogeny for New Zealand sheet-web spiders (Cambridgea) and comparison of web-building behaviour

ABSTRACT Spider webs vary in size to meet the nutritional requirements of the resident spider with the resident’s body size strongly informing these requirements. In this way, the effect of body size on web-building behaviour should be apparent across species. To determine whether the size of analogous web structures scales with body size across closely related species, we first measured mainsheet area and adult female body size of 12 sheet-web spider species (Cambridgea). Using these species, we then generated alignments from the cytochrome c oxidase subunit I (COI) and histone 3 (H3) gene regions. These alignments were phylogenetically analysed using Bayesian inference and maximum likelihood methods. While phylogenetic trees for the COI gene suggested that Cambridgea is monophyletic relative to sampled outgroups, H3 did not. Combining our COI phylogenetic tree’s branch lengths with data on web-building behaviour, we used phylogenetic least squares to determine whether web size scales with spider size across species. While we found evidence that larger species generally build larger webs, the variation in web size across even similarly sized species suggests that environmental characteristics which influence site selection and prey type may play a role in determining the optimal web size for different species.

Evaluation of manipulative effects by an ichneumonid spider-ectoparasitoid larva upon an orb-weaving spider host (Araneidae: Cyclosa argenteoalba) by means of surgical removal and transplantation

Surgical removal and larval transplantation experiments were carried out to evaluate behavioral manipulative effects caused by larvae of the polysphinctine ichneumonid, Reclinervellus nielseni (Roman, 1923), on its orb-weaving spider host, Cyclosa argenteoalba Bösenberg & Strand, 1906 (Araneidae). Residual behavioral effects on spiders from which parasitoid larvae had been removed were recognized and are described. Some transplanted parasitoid larvae also successfully consumed alternative spider hosts provided to them, and completed metamorphosis. The removal experiment supports previous hypotheses proposed by Eberhard, that larval effects involve chemicals, which are still unidentified and are dosage-dependent, because (1) spiders with parasitoid larvae removed continued to show manipulated behavior, and (2) the later in their development that the parasitoid larvae were removed, the more acute remaining effects were (e.g., production of V radii, new hub loops and silk decorations on webs). Further, the results support the idea that the spider's web-building behavior is composed of independent units (modules), because whether or not specific web features were produced depended on when the larva was removed. Transplantation experiments provide a new technique for rearing parasitoid larvae whose host spider dies: penultimate instar parasitoid larvae were successfully reared following their removal from their original host by providing them with another host spider held by a mesh. Transplantation of a small young larva by gluing it onto another host that was released after successful transplantation, caused the new host to produce a modified web identical to the “cocoon” webs typically produced by parasitized spiders. This shows that venom injected by the adult parasitoid prior to oviposition is not necessary to induce behavioral changes in the host, which can be caused entirely by wasp larval secretions.

Urban heat island conditions experienced by the Western black widow spider (Latrodectus hesperus): Extreme heat slows development but results in behavioral accommodations.

While shifts in organismal biology stemming from climate change are receiving increased attention, we know relatively little about how organisms respond to other forms of anthropogenic disturbance. The urban heat island (UHI) effect describes the capture of heat by built structures (e.g. asphalt), resulting in elevated urban temperatures. The UHI is a well-studied phenomenon, but only a handful of studies have investigated trait-based shifts resulting from the UHI, and even fewer have attempted to quantify the magnitude of the UHI experienced at the microclimate scale. Here, using a common urban exploiter, the Western black widow spider (Latrodectus hesperus), we show that the UHI experienced by spiders in July in their urban Phoenix, AZ refuges is 6°C hotter (33°C) than conditions in the refuges of spiders from Sonoran Desert habitat outside of Phoenix’s development (27°C). We then use this field microclimate UHI estimate to compare the development speed, mass gain and mortality of replicate siblings from 36 urban lineages reared at ‘urban’ and ‘desert’ temperatures. We show that extreme heat is slowing the growth of spiderlings and increasing mortality. In contrast, we show that development of male spiders to their penultimate moult is accelerated by 2 weeks. Lastly, in terms of behavioral shifts, UHI temperatures caused late-stage juvenile male spiders to heighten their foraging voracity and late-stage juvenile female spiders to curtail their web-building behavior. Trait-based approaches like the one presented herein help us better understand the mechanisms that lead to the explosive population growth of urban (sometimes invasive) species, possibly at the expense of urban biodiversity. Studies of organismal responses to the present day UHI can be used as informative surrogates that help us grasp the impact that projected climate change will have on biodiversity.

Predator chemical cues decrease attack time and increase metabolic rate in an orb-web spider.

Animals are able to assess the risk of predation and respond accordingly via behavioural and physiological changes. Web-building spiders are in the unique situation where they reside in the middle of their web and are therefore relatively exposed to predators. Thus, these spiders might moderate either their web-building behaviour or their behaviour on the web when exposed to the threat of predation. In this study, we experimentally explored how chemical cues from a predator influence foraging behaviour and metabolic rate in females of the orb-web spider Argiope keyserlingi We found that female spiders restricted their foraging time budget when exposed to the predator cues from a praying mantid: they responded 11% and 17% quicker to a vibratory stimulus compared with control and non-predator cues, respectively, and spent less time handling the prey. Moreover, spiders were less likely to rebuild the web under predator cues. Female A. keyserlingi exposed to the praying mantid cue significantly elevated their metabolic rate compared with the control group. Our findings revealed short-term modifications over the 2week trials in foraging behaviour and the physiology of female spiders in response to predator cues. This study suggests that under predator cues the spiders move quicker and this could be facilitated by elevation in metabolic rate. Reduced foraging activity and less frequent web repair/rebuilding would also reduce the spiders' exposure to praying mantid predators.

On the development of a predictive functional trait approach for studying terrestrial arthropods.

The characterization of ecological communities with functional traits allows to consider simultaneously the ability of a species to survive and reproduce in an environment, its interactions with other species and its effects on the ecosystem. Functional traits have been studied mainly by plant ecologists, but are increasingly common in the study of other taxa including arthropods. Arthropods represent a group for which a functional trait approach could be highly profitable because of their high diversity, abundance, ubiquity and role in many important ecological processes. This review synthesizes two decades of functional trait research on terrestrial arthropods. We show that while the approach has gained popularity, particularly in the last decade, the absence of clearly postulated hypotheses is a recurrent problem limiting generalization. Furthermore, studied traits are often poorly related to studied functions. To address these problems, we propose a step-by-step protocol to postulate clear hypotheses prior to trait selection and emphasize the need for a common set of more generalizable traits in future studies. Extending the functional trait approach to arthropods opens the door to improving our understanding of interspecific interactions and potential links between response and effect traits. We present the concept of trait-matching with several examples of arthropod traits known to be effective predictors of consumer-resource interactions. The development of a successful functional trait approach for terrestrial arthropods will necessitate an understanding of relevant traits, standardized measurement protocols and open access databases to share this information. Such progress will provide ecologists with a new set of tools to answer broad questions in several fields including the study of community assembly, ecological networks and multitrophic functionality.

Automatic segmentation of gallbladder using bio-inspired algorithm based on a spider web construction model

In medical image processing, an accurate segmentation and classification are very important and this field still needs an effective computer-based algorithm for accomplishing the task. In gallbladder segmentation, only few automatic segmentation methodologies have been presented. The accuracy is very important in medical image processing for accurate diagnosis of the disease. In this paper, by exploiting the basic web building behavior of spiders, we developed a bio-inspired algorithm based on the spider web construction process for image segmentation process in medical images. The aim of this paper is to detect the shape of the gallbladder and to segment the gallstones and polyps located inside the gallbladder using a computer-based algorithm. It is necessary to apply a suitable preprocessing method in order to eliminate the irregularities presenting in the ultrasound scan images. In the preprocessing stage, histogram equalization and DooG filter are applied to enhance the contrast of the image. After that, the proposed spider web algorithm is applied in the segmentation process. The performance metrics of the proposed method are evaluated by implementing the proposed method to test the input dataset of 60 patients and it is compared with the results obtained from conventional segmentation methods. The values of DSC, OF, OV and PE for images with no lesions are 0.873167, 0.8389, 0.81705 and 0.81452.

The parasitoid wasp Eruga unilabiana Pádua & Sobczak, sp. nov. (Hymenoptera: Ichneumonidae) induces behavioral modification in its spider host

AbstractSome polysphinctine parasitoid wasps can alter the web building behavior of their host spiders. In this paper, we describe and illustrate a new species Eruga unilabiana sp. nov. and report for the first time, to the best of our knowledge, the interaction between this parasitic wasp and the linyphiid spider Dubiaranea sp. We investigated the wasp's host selection, development, and manipulation of host behavior. We found that most of the parasitized spiders were intermediate‐sized adult females that probably provide sufficient resources for parasitoid larvae and are less vulnerable for parasitoid females than larger host individuals at attack. The cocoon web of Dubiaranea sp. consists of a complex three‐dimensional tangle structure with several non‐stick radial lines that converge at the cocoon. In addition, E. unilabiana individuals construct their cocoons horizontally, which differ from cocoons of the majority of polysphinctine wasps. This study provides important information and discussion to further understand the evolution of parasitoid wasp–spider interactions.

The Effect of Wind Exposure on the Web Characteristics of a Tetragnathid Orb Spider

Studies on spiders in their natural habitats are necessary for determining the full range of plasticity in their web-building behaviour. Plasticity in web design is hypothesised to be important for spiders building in habitats where environmental conditions cause considerable web damage. Here we compared web characteristics of the orb spider Metellina mengei (Araneae, Tetragnathidae) in two different forest habitats differing in their wind exposure. We found a notable lack of differences in web geometry, orientation and inclination between webs built along an exposed forest edge and those built inside the forest, despite marked differences in wind speed. This suggests that M. mengei did not exhibit web-building plasticity in response to wind in the field, contrasting with the findings of laboratory studies on other species of orb spiders. Instead, differences in prey capture and wind damage trade-offs between habitats may provide an explanation for our results, indicating that different species employ different strategies to cope with environmental constraints.

Proximate mechanism of behavioral manipulation of an orb-weaver spider host by a parasitoid wasp.

Some ichneumonid wasps induce modifications in the web building behavior of their spider hosts to produce resistant “cocoon” webs. These structures hold and protect the wasp’s cocoon during pupa development. The mechanism responsible for host manipulation probably involves the inoculation of psychotropic chemicals by the parasitoid larva during a specific developmental period. Recent studies indicate that some spiders build cocoon webs similar to those normally built immediately before ecdysis, suggesting that this substance might be a molting hormone or a precursor chemical of this hormone. Here, we report that Cyclosa spider species exhibiting modified behavior presented higher 20-OH-ecdysone levels than parasitized spiders acting normally or unparasitized individuals. We suggest that the lack of control that spiders have when constructing modified webs can be triggered by anachronic activation of ecdysis.