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Proportion of experiments in which the balls emerged (y) after a cumulative flow of x mites. The curve presents a threshold (s = 259.4 mites). A logistic function (solid line) was fitted to our experimental data (dots) with a logistic regression. doi:10.1371/journal.pone.0018854.g003

Proportion of experiments in which the balls emerged (y) after a cumulative flow of x mites. The curve presents a threshold (s = 259.4 mites). A logistic function (solid line) was fitted to our experimental data (dots) with a logistic regression. doi:10.1371/journal.pone.0018854.g003

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Tetranychus urticae is a phytophagous mite that forms colonies of several thousand individuals. These mites construct a common web to protect the colony. When plants become overcrowded and food resources become scarce, individuals gather at the plant apex to form a ball composed of mites and their silk threads. This ball is a structure facilitating...

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... balls emerged, however, some of the mites started to get trapped at the top of the stick, favouring the growth of the silk ball. The relationship between the moment of emergence of the silk balls and the cumulated flow appeared when looking at the proportion of the experiments in which the ball has emerged, as a function of the cumulated flow (Fig. 3). The cumulated flow was proportional to the number of mites that had passed to the top of the stick since the beginning of the experiment. Since mites always spin silk while walking, the cumulated flow was also an indicator of the quantity of silk that had accumulated on the top of the wooden stick. The curve was clearly sigmoidal, ...
Context 2
... needed to be a critical quantity of silk on the top for the first mites to stay and start forming the ball. In order to quantify the phenomenon, we performed a logistic regression (equation 3) with the cumulated flow as the independent variable and the presence or absence of a ball as the binary dependent variable. The logistic curve (equation 3, Fig. 3) expressed the proportion of experiments in which a silk ball was present (y), according to the cumulated flow ...

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... 29 Furthermore, when crowded, T. urticae forms silk balls at the plant apex, aiding group dispersal by wind or animals. 30 This positive phototaxis may benefit the specialized spider mite predator P. persimilis by moving to brighter habitats (i. e. the upper stratum of the host plant), thereby increasing its chances of locating prey independently of prey cues. ...
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BACKGROUND Phototactic behavior and oviposition site selection in phytoseiid predators are crucial for understanding their ecological interactions and optimizing their use in agricultural pest management. This study investigated the phototactic responses and oviposition preferences of seven phytoseiid species of proven or potential importance in biocontrol: Amblydromalus limonicus (Garman & McGregor), Amblyseius herbicolus (Chant), Amblyseius lentiginosus Denmark and Schicha, Neoseiulus barkeri Hughes, Neoseiulus cucumeris (Oudemans), Neoseiulus womersleyi (Schicha), and Phytoseiulus persimilis Athias‐Henriot. We hypothesized that these phytoseiid predators use light as a cue, with their phototactic behavior aligning with their respective lifestyles. RESULTS By presenting adults of these species with two choices (i.e. light and dark) in acrylic arenas, we found that P. persimilis exhibited a significant preference for light. In contrast, other species showed no phototactic preference. The phototactic preferences were similar between genders of all six sexually reproducing species tested in this study. Furthermore, the oviposition site preferences varied significantly among species. Gravid females of As. herbicolus, N. cucumeris, N. womersleyi, and P. persimilis preferred dark sites for egg laying, whereas Ad. limonicus and As. lentiginosus showed no light preference, and N. barkeri preferred light for oviposition. CONCLUSION This study highlights the importance of light as an ecological factor influencing phytoseiid behavior and suggests that phototactic and oviposition preferences are adaptations to specific environmental niches. These findings have practical implications for enhancing the effectiveness of phytoseiids in pest management. Further research should investigate the mechanisms driving phototactic responses and light perception in these phytoseiid predators. © 2024 Society of Chemical Industry.
... It can feed about 1200 plant species of which over a hundred are of agricultural importance including soybean, tomatoes, cucumber, cotton, leafy greens, etc. [3][4]. This pest is characterized by rapid multiplication, reduced development time, and a high adult survival rate [5], making it notorious among the pests. Consumption of the host plant by the pest, results in the reduction of leaf surface area for photosynthesis, as they develop chlorotic and necrotic spots after infestation. ...
Article
Tetranychus urticae (two-spotted spider mite) is a pest infesting multiple crops of agricultural importance. An effective remedy for the prevention and control of this pest is lacking. This study focuses on the preparation and identification of the phytocompounds from the indigenous bioformulation by GC-MS analysis. Further, the identified compounds were targeted against the proteins present in the reproductive cycle of the pest by molecular docking. Molecular docking analysis revealed an effective binding score against the vital proteins which will be effective in arresting the multiplication of the two-spotted spider mites. Since the phytocompound affect the reproductive proteins, its further multiplication and spread in the field can be averted. The current in silico study depicts the interaction of the mite protein and the phytocompound which also effective against other pests. This is a first ever report for the characterization of the bioformulation against pests from this region.
... Web-building was assessed when mites swaying their forelegs in a side-to-side motion and observation of threads of silk fibers left on the leaf surface 25 . Note that there is variation in the types of web structures produced by spider mites from silk threads and balls to more extensive silk production similar to a nest with eggs and spider mites 37 . Here, the midrib of the leaf, where spider mites are primarily found with extensive web structures on maize plants, was not a part of the arena owing to requirements for imaging (a flat leaf surface) and therefore limited the ability to evaluate extensive web-building. ...
... Among major arthropod herbivores of maize, the web-spinning capability of spider mites is unique, and is known to serve many purposes such as protection from natural enemies and acaricides, mate finding, locomotion and dispersal and colonization [23][24][25]37,41 . The amount of silk produced in the web-spinning behavior of mites depends on temperature, air humidity, smoothness of substrate, plant species and other unknown factors [23][24][25]37 . ...
... Among major arthropod herbivores of maize, the web-spinning capability of spider mites is unique, and is known to serve many purposes such as protection from natural enemies and acaricides, mate finding, locomotion and dispersal and colonization [23][24][25]37,41 . The amount of silk produced in the web-spinning behavior of mites depends on temperature, air humidity, smoothness of substrate, plant species and other unknown factors [23][24][25]37 . In our study, TSM web-building was increased on B75 and B96 as compared to B73. ...
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Plants are attacked by diverse herbivorous pests with different host specializations. While host plant resistance influences pest pressure, how resistance impacts the behaviors of generalist and specialist herbivores, and the relationship to resistance, is less well known. Here, we investigated the short-term (< 1 h) behavioral changes of a generalist herbivore, the two-spotted spider mite (TSM), and a specialist herbivore, the Banks grass mite (BGM), after introduction to no-choice Tanglefoot leaf-arenas (2 × 2 cm) of three maize inbred lines (B73, B75, and B96). The widely-used inbred line B73 is susceptible to spider mites, while B75 and B96 are known to be mite resistant, especially to TSM. Video tracking was used to record TSM and BGM walking, probing, feeding, resting, web-building and travel distance on arenas of each line. Mite oviposition was also recorded after 72 h. B75, a resistant line, decreased the feeding behavior (i.e., time) of both mite species compared to B73 (susceptible control) and B96. Moreover, TSM appeared to be sensitive to both resistant lines (B75 and B96) with reduced oviposition, and increased resting and web-building times compared to susceptible B73. In contrast, the specialist BGM showed no difference in oviposition, resting and web-building time across all maize inbred lines. Our findings of quite broad and short-term responses of TSM to B75 and B96 are consistent with a role for constitutive or rapidly induced plant defenses in maize in conferring TSM resistance. Other mechanisms of plant resistance may be needed, however, for defense against specialists like BGM.
... The dense webs may protect mites from predation (McMurtry et al. 1970;Sabelis 1985;Tien et al. 2009;Dittmann and Schausberger 2017), bad weather conditions (Davis 1952;Linke 1953) and pesticides (McMurtry et al. 1970) and serve as modes of dispersal (Saito 1977;Gerson 1985;Yano 2008;Clotuche et al. 2013b). Additionally, silk may act as the substrate for sex pheromones (McGregor 1950;Saito 1977Saito , 1979Sabelis 1985;Sabelis and Bakker 1992;Zhang et al. 2002;Yano 2008;Clotuche et al. 2009Clotuche et al. , 2011Clotuche et al. , 2012bClotuche et al. , 2014Tien et al. 2009;Le Goff 2011). Moreover, as spinning silk is costly due to energy and protein expenditure (Hazan et al. 1974), mothers living on leaves over which silk is already present may minimize their silk production and allocate more resources to reproduction (Oku et al. 2009;Le Goff et al. 2010) and survival (Le Goff et al. 2010;Yano 2012). ...
... Spider mites usually colonize and feed on the underside of leaves of host plants by piercing cells and extracting cell contents (Dhooria 2016), leading to scramble competition for food resources (Krips et al. 1998). Aggregating in a habitat may induce overcrowding conditions which will accelerate food depletion in the natal environment (Krips et al. 1998;Clotuche et al. 2011;Bitume et al. 2013). Therefore, females must develop strategies to minimize resource competition with conspecifics and their offspring. ...
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Selection of a suitable habitat by animals before settlement is critical for their survival and reproduction. In silk-spinning arthropods like spider mites, denser webs offer protection from predation and serve as a dispersal mode. Settling in habitats with the presence of conspecifics and silk webs can benefit the habitat-searching females. Silk and conspecifics usually coexist, but their distinct effects on female colonization have received little attention. In this study, we used a haplodiploid spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), to examine the impact of conspecific cues, including cues from ovipositing conspecifics and silk, on habitat selection and subsequent reproductive performance of females. Results show that females significantly preferred habitats with cues from neighboring conspecifics and silk and neighboring conspecifics induced additive effect to that of silk on habitat selection. Conspecific cues did not boost female reproduction but facilitated females laying larger eggs that were more likely to be fertilized and to develop into daughters. When given a choice between silk-covered and clean habitats, females preferred silk-covered habitats, laid a similar number of eggs with similar size, but produced more daughters, suggesting that T. ludeni females can adjust the size threshold for fertilization in response to the current social environment. Knowledge of this study improves our understanding of spider mite habitat selection and post-settlement reproductive performance behaviors.
... The two-spotted spider mites are a member of a group of mites that spin webs, and the name "spider" underscores its capacity to create webbing that resembles silk. They were typically hidden beneath the webs, which serve as a vehicle for dispersal, shelter from predators, a suitable microhabitat for the TSSM, protection against abiotic agents, and a means of communication (Le Goff et al., 2010;Clotuche et al., 2011;Muluken et al., 2016;Gebissa et al., 2019). ...
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The study sought to ascertain spider mite prevalence, infestation, and identification and to assess the response of potato genotypes. In 2022, this pest was only observed on some genotypes in December. In late January, an infestation, incidence, and severity increased from 10 to 13 genotypes on potato tuber stocks stored for irrigation experiments. Those genotypes were planted in irrigated fields, and the sprouted tuber losses ranged from 12.5% to 100% and up to 15.38% in the 2022 and 2023 records, respectively. Following this, spider mites, often known as two-spotted spider mites (TSSM) or Tetranychus urticae, were identified. This is the first time a potato sprout infestation has been recorded in Ethiopia. The two-spotted spider mites damaged the tubers quantitatively by sucking the moisture of sprouts up to the 5th grade, with 97 and >75% infestation levels, incidence, and severity, respectively. The pest grows very rapidly and hastens the drying of sprouted tuber leaves. Some genotypes were resistant to TSSM and recovered after the sprouts were infected and dried, which were treated with pesticides in 2023. The typical agricultural insecticides were ineffective in controlling the pest in the first year, and a Profenofos was applied in the second year. Thus, seed tubers are the main production limit unless appropriate research efforts are undertaken and management techniques are created. Int. J. Agril. Res. Innov. Tech. 13(2): 55-63, Dec 2023
... It can feed about 1200 plant species of which over a hundred are of agricultural importance including soybean, tomatoes, cucumber, cotton, leafy greens, etc. [3][4]. This pest is characterized by rapid multiplication, reduced development time, and a high adult survival rate [5], making it notorious among the pests. Consumption of the host plant by the pest, results in the reduction of leaf surface area for photosynthesis, as they develop chlorotic and necrotic spots after infestation. ...
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Tetranychus urticae (two-spotted spider mite) is a pest infesting multiple crops of agricultural importance. An effective remedy for the prevention and control of this pest is lacking. This study focuses on the preparation and identification of the phytocompounds from the indigenous bioformulation by GC-MS analysis. Further, the identified compounds were targeted against the proteins present in the reproductive cycle of the pest by molecular docking. Molecular docking analysis revealed an effective binding score against the vital proteins which will be effective in arresting the multiplication of the two-spotted spider mites. Since the phytocompound affect the reproductive proteins, its further multiplication and spread in the field can be averted. The current in silico study depicts the interaction of the mite protein and the phytocompound which also effective against other pests. This is a first ever report for the characterization of the bioformulation against pests from this region.
... As far as it is known, among the acariform mites only the terrestrial bdellids (Bdellidae) use their silk for capturing prey (Alberti and Ehrnsberger 1977) fastening it to the ground using their threads. Other terrestrial acariform mites studied so far-the actively spinning tetranychids (Tetranychidae) and eriophyids (Eriophyidae)-use silk for protection of the colony and for dispersal, not for hunting because these mites are associated with plants (Manson and Gerson 1996;Clotuche et al. 2011). Unfortunately, the exact function of silk Fig. 7 Scanning electron microscopy (SEM) of 'naturally' produced silk in the freshwater mite Limnesia maculata. ...
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The structural characteristics of silk secretion of the freshwater mite Limnesia maculata (O.F. Müller) (Acariformes, Limnesiidae) are described and analyzed for the first time based on light, atomic force and electron-microscopical approaches. The common dermal glands (14 pairs scattered over the body) produce silk mostly during the warm summer season. The process of silk secretion lasts from several hours to several days. The silk may appear like barely recognized clouds of a fine whitish substance. An individual silk thread is an indefinitely long uniform unbranched and non-stretchable tube, hollow or with a vesicular electron-dense residual content. In the silk bundle, threads may be freely interlaced, bent, curved or occasionally broken. The diameter of the tubes is in the range of 0.9–1.5 µm. The width of the tube walls varies greatly from 60 to 300 nm. Chaotically interlaced fine fibrils build the tube walls. On the external surface of the tube wall, these fibrils are loosely organized and frequently rising vertically, whereas on the internal side they are packed more tightly sometimes showing a mesh. The walls may reveal a layered structure or, contrary, are quite thin with through foramens. The revealed organization of silk in the freshwater mites is found to be the simplest among that of other arthropods. We propose a role of the silk in the capture of potential prey in the summer season. Silk in water mites significantly widens the wholesome area for the mites' life and gives them better chances in competition for potential resources.
... Increase the amount of resource consumed per capita Capturing a larger fraction of prey group bubble-net feeding in humpback whales (Jurasz and Jurasz 1979), ospreys (Greene 1987), leaf-notching moths (Tsubaki and Shiotsu 1982), black-headed gulls (Götmark et al. 1986), blue tang surgeonfish (Foster 1985), orcas (Bigg et al. 1987) Moving more efficiently grey mullet (Marras et al. 2015), ducklings paddling on water (Fish 1995), great white pelicans in flight (Weimerskirch et al. 2001), aquatic crustaceans (Ritz 2000) Collective energetics Decrease rate of energy expenditure Spending less energy on homeostasis emperor penguins (Ancel et al. 2015), honeybees (Kronenberg and Heller 1982), big brown bats (Willis and Brigham 2007), cavies (Taraborelli and Moreno 2009) Moving away from current environment faster Mormon crickets (Berdahl et al. 2018, Romanczuk et al. 2009, Simpson et al. 2006, colonial salps (Sutherland and Weihs 2017), fruiting-body-assisted dispersal in Dictyostelium (Gadagkar andBonner 1994, smith et al. 2014) and Myxococcus bacteria (Shimkets 1999), spider mites (Clotuche et al. 2011) Accessing collective benefits while dispersing storks locating thermals This is the author's accepted manuscript without copyediting, formatting, or final corrections. It will be published in its final form in an upcoming issue of The American Naturalist, published by The University of Chicago Press. ...
Article
From biofilms to whale pods, organisms across taxa live in groups, thereby accruing numerous diverse benefits of sociality. All social organisms, however, pay the inherent cost of increased resource competition. One expects that when resources become scarce, this cost will increase, causing group sizes to decrease. Indeed, this occurs in some species, but there are also species for which group sizes remain stable or even increase under scarcity. What accounts for these opposing responses? We present a conceptual framework, literature review, and theoretical model demonstrating that differing responses to sudden resource shifts can be explained by which sociality benefit exerts the strongest selection pressure on a particular species. We categorize resource-related benefits of sociality into six functionally distinct classes and model their effect on the survival of individuals foraging in groups under different resource conditions. We find that whether, and to what degree, the optimal group size (or correlates thereof) increases, decreases, or remains constant when resource abundance declines depends strongly on the dominant sociality mechanism. Existing data, although limited, support our model predictions. Overall, we show that across a wide diversity of taxa, differences in how group size shifts in response to resource declines can be driven by differences in the primary benefits of sociality.
... As far as is known, among the acariform mites only the terrestrial bdellids (Bdellidae) use their silk for capturing prey (Alberti and Ehrnsberger 1977) fastening it to the ground by their threads. Other terrestrial acariform mites studied so far -the actively spinning tetranychids (Tetranychidae) and eriophyids (Eriophyidae) -use silk for protection of the colony and for dispersal, not for hunting because these mites are associated with plants ( Manson and Gerson 1996;Clotuche et al. 2011). Unfortunately, the exact function of silk in water mites remains unclear. ...
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Full-text available
The structural characteristics of silk secretion of the freshwater mite Limnesia maculata (O.F. Müller, 1776) (Acariformes, Limnesiidae) are described and analyzed for the first time based on light, atomic force and electron-microscopical approaches. The common dermal glands (14 pairs scattered over the body) produce silk mostly during the warm summer season. The process of silk secretion occupies from several hours to several days. Silk may be detected as barely recognized clouds of a fine whitish substance. An individual silk thread is an infinitely long uniform unbranched and non-stretchable tube, hollow or with a vesicular electron-dense residual content. In the silk bundle, threads may be freely interlaced, bent, curved or occasionally broken. The diameter of the tubes mostly lies within 0.9–1.5 µm. The width of the tube walls varies greatly from 60 to 300 nm. Chaotically interlaced fine fibrils build the tube walls. On the external surface of the tube wall, these fibrils are loosely organized and frequently rising vertically, whereas on the internal side they are packed more tightly sometimes showing a mesh. The walls may reveal a layered structure or, contrary, are quite thinner with through foramens. The revealed organization of silk in the freshwater mites is found to be the simplest among that of other arthropods. The proposed role of such silk is a capture of the potential prey in the summer season. Silk in water mites significantly widen the wholesome area for their life and gives them better chances in competition for potential resources.
... In addition to reproductive capacity, it is conceivable that females have certain physical advantages over males and immatures, in that the larger body dimensions of adult female R. indica may be more conducive to dispersal by aiding exit from the laminar boundary layer by facilitating exposure to higher wind speeds (Smitley and Kennedy 1985;Cho et al. 2018). The aerial dispersal of immatures has also been verified in the mite Tetranychus urticae Koch (Acari: Tetranychidae) based on observation in arenas with a window fan (Smitley & Kennedy 1985) and mainly composing the interior of silk balls of T. urticae (98.9% of subjects were immature) and Tetranychus ogmophallos Ferreira and Flechtmann (78,2% of subjects were immature) (Clotuche et al. 2011;Santos et al. 2020). ...
... For tetranychids, dispersal increased at high population density, but the tests show the influence of density as an indirect effect of dispersal, being mainly influenced by the conditions of the host plant (Smitley & Kenedy 1988;Li & Margolies 1993). For these mites, a high population density is related to a rapid depletion of the host, which leads to the process described as the formation of mite balls (Clotuche et al. 2011 (Congdon & Logan 1983), and generally deplete the host in a very gradual manner than what is observed in spider mites (personal observation). Therefore, the relationship between population density and host depletion is difficult to compare with tetranychids. ...
Article
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Aerial dispersal can occur in response to both internal state of individuals and environmental conditions and probably contributed to the expansion of red palm mite Raoiella indica throughout the American continent within a decade. We report here experiments using wind tunnel in the laboratory and adhesive traps in the field to identify general aspects and precursors of R. indica’s aerial dispersal. Wind tunnel analyses indicated that dispersal rates increased with increasing wind speed up to 15 m/s and decreased with increasing population density. Although adult male and immature were dispersed by wind, adult females showed the highest frequency of dispersal. Mating status and 24 h food deprivation had no significant influence on the aerial dispersal of this species. In the field, the dispersal was also mainly observed among adult females. The number of captured mites increased progressively with height, up to the highest assessed state (4.8 m), and up to a distance of 48 m from infested coconut palms, at which colonization rates were equivalent to 1.4 × 105 mites/plant, although it was lower at the distance of 64 m (farthest assessed distance) from the source. The results identify conditions that elicit R. indica’s dispersal, and characterize its dispersal potential and colonization rates, allowing an ecological understanding of this invasive mite species.