Leucauge Venusta Research Articles

Water harvesting during orb web recycling

Before constructing an orb web, an araneoid spider takes down and ingests the previous day's web. Nocturnal species do this either during the early evening or in the early morning and diurnal species during the early morning, times of the day when relative humidity (RH) is high. Under these conditions the hygroscopic glue droplets of a web's viscous prey capture thread attract atmospheric moisture, providing a net gain of water when a spider ingests its web. The contribution of web recycling to a spider's water budget has been estimated, but not determined empirically. This study does so for adult females of four species (Araneus marmoreus Clerck, 1757, Argiope trifasciata (Forskål, 1775), Leucauge venusta (Walckenaer, 1841), and Micrathena gracilis (Walckenaer, 1805)) by first determining the total volume of a web's glue droplets at 20% and 37% RH to estimate the water invested in web during construction. Subtracting each of these values from the web's total droplet volume at 90% RH approximates the range of water harvested when the web is recycled. High estimates of the net water gained range from 0.45% of a spider's body mass (3.01 µl water gained) in A. marmoreus to 0.88% of body mass (0.19 µl water gained) in L. venusta. In A. trifasciata, the water gained when a web is ingested is equivalent to 29% of a spider's daily evaporative water loss.

Starvation Time and Predatory Efficiency of Spider Species on Bemisia tabaci (Homoptera: Aleyrodidae)

Four predatory spider species, Leucauge venusta (Orchard) (Araneae: Tetragnathidae), Lycosa pseudoannulata (Boeset) (Araneae: Lycosidae), Larinioides cornutus (Clerck) (Araneae: Araneidae), and Tetragnatha shikokiana (Yaginuma) (Araneae: Tetragnathidae), were used to control Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in the laboratory and greenhouse, and their longevity without food was observed. For the laboratory experiment, the spiders' feeding capabilities were checked at 1, 4, 8, and 16 h of exposure in a 10 mL vial containing 50 five-d-old whiteflies. For the greenhouse experiment, the preys' feeding ability was recorded at 24 and 48 h, with 100 five-d-old adult whiteflies in a screened cage. Individual spiders were kept in the lab in 10 mL vials, and their survival time was recorded every 5 h. Of the 4 spider species, L. pseudoannulata was the most active in the lab and consumed an average of 3.00 ± 0.22, 6.17 ± 0.27, 9.67 ± 0.43, and 13.50 ± 0.49 at 1, 4, 8, and 16 h of the bioassay, followed by L. venusta, L. cornutus, and T. shikokiana. However, in the greenhouse experiment, L. venusta consumed the greatest number of whiteflies, with an average of 24.66 and 51.33 (out of 100) at 24 and 48 h, respectively, followed by L. pseudoannulata, L. cornutus, and T. shikokiana. The maximum longevity was recorded for L. venusta with 26.67 h, followed by T. shikokiana, L. pseudoannulata, and L. cornutus without prey. All spider species killed and consumed adult whiteflies in both experiments, which suggests that they are a controlling tool in the natural ecosystem. The results from our experiment will contribute to the biological control of whitefly.

Orchard Orbweaver, Orchard Spider Leucauge argyrobapta (White), Leucauge venusta (Walckenaer) (Arachnida: Araneae: Tetragnathidae)

The orchard orbweavers, Leucauge argyrobapta (White) (Figure 1) and Leucauge venusta (Walckenaer), are attractive small spiders and collectively are some of the most common spiders in the eastern U.S. The name orchard orbweaver is the common name accepted by the American Arachnological Society Committee on Common Names of Arachnids (Breen 2003) for these species, but they have also been called simply orchard spiders (Kaston & Kaston 1953, Levi & Levi 2002). Orchard orbweavers belong to the family Tetragnathidae, the longjawed orbweavers (Levi & Hormiga 2017, World Spider Catalog 2018).
 This document describes its synonymy and nomenclature, distribution, description, behavior, and enemies. Also available on the Featured Creatures website at http://entomology.ifas.ufl.edu/creatures.
 https://edis.ifas.ufl.edu/in1243

Diversidad espacial y temporal de arañas en microhábitats de cultivos de Citrus sinensis, (Rutaceae) Corrientes, Argentina

We analyze the distribution of spider assemblages at three microhabitats (canopy, tree trunk and soil) in Citrus sinensis orchards (Rutaceae) in the Province of Corrientes, Argentina. Spiders were collected monthly using four sampling techniques: beating foliage, leaf litter sifting, pitfall traps and direct capture by hand. A total of 2160 samples were examined and 7194 spiders were collected (2462 on the canopy, 983 on trunk and 3749 on the floor) belonging to 34 families and 200 species/morphospecies of Araneomorphae. There were significant differences among microhabitats and months in the structure of the spider communities, according to analysis of similarity (ANOSIM). The diversity was highest on the canopy, followed by soil and tree trunk. Araneidae, Salticidae and Anyphaenidae were the most abundant taxa in the canopy; the dominant species were Jessica erythostoma and Cheiracanthium inclusum, a predator of the leaf herbivore Phyllocnistis citrella (Lepidoptera) a pest of Citrus spp. The most abundant families on the tree trunk were Tetragnathidae, Hersiliidae and Theridiidae, Iviraiva pachyura was a species specialist in such microhabitat; and Leucauge venusta was an opportunistic species, because their abundance increaseds markedly in anthropic environments that modified by man. The most abundant families on the floor were Lycosidae, Linyphiidae and Coriniidae. In this habitat, Lycosa erythrognatha and Pardosa plumipedata were dominant species. The Chao-Jaccard similarity index was highest between the canopy and trunk (J-C=0.95), likewise ordination by nonmetric multidimensional scaling (NMDS) revealed strong differentiation between assemblages of soil spiders and canopy and trunk spiders. Also, on the soil the temporary replacement of species was greater and the seriation method was significant (z=3.82, p=0.00) therefore there was a succession of species during the year. The different species in each microhabitat probably avoided competition by using different hunting strategies and different ecological resources, in addition to specific patterns of temporal distribution. Our results suggest that anthropic environments, such as in Citrus orchards, tend to harbor populations of spiders able to adapt to those environments and interact in a balanced way in space and time.

Species delimitation of the North American orchard-spider Leucauge venusta (Walckenaer, 1841) (Araneae, Tetragnathidae)

The orchard spider, Leucauge venusta (Walckenaer, 1841) is one of the most common and abundant orb-weavers in North America. This species has a broad geographic distribution extending across tropical and temperate regions of the Americas from Canada to Brazil. Guided by a preliminary observation of the barcode gap between sequences from specimens of L. venusta collected in Florida and other North American localities, we collected across a transect through the southeastern USA to investigate the observed genetic divide. The dataset, complemented with additional samples from Mexico, and Brazil was analyzed for species delimitation using STACEY and bGMYC based on sequences from one nuclear (ITS2) and one mitochondrial marker (COI). The analyses clearly separate USA samples into two deeply divergent and geographically structured groups (north–south) which we interpret as two different species. We generated ecological niche models for these two groups rejecting a niche equivalence hypothesis for these lineages. Taxonomic changes are proposed based on these findings, Leucauge venusta is restricted to denote the northern clade, and its known distribution restricted to the USA. Leucauge argyrobapta (White, 1841) is removed from synonymy to denote the populations in Florida, Mexico and Brazil. Although the delimitation analyses suggest each of these geographic clusters within the L. argyrobapta samples represent different species, more specimens from Central and South America are needed to properly test the cohesion of L. argyrobapta populations.

Variation in web-building spider communities among three tropical tree species in a young experimental plantation

Abstract We documented the presence and abundance of spider species (Arachnida: Araneae) on young trees of Swietenia macrophylla, Ceiba pentandra and Cordia dodecandra found in an experimental plantation. Surveys of spider abundance and species identity conducted twice during the growing season indicated marked differences in web-building spider assemblages associated with each tree species. Swietenia exhibited the lowest spider abundance, whereas Cordia and Ceiba had similarly higher abundances. Leucauge venusta (Walckenaer, 1841) was the dominant spider on all tree species, but different spider species were co-dominant on Cordia and Ceiba (Araneus pegnia (Walckenaer, 1841) and Argiope argentata (Fabricius, 1775) respectively), and several spider species were exclusive to each tree species. These results highlight the influence of tree species identity on community structure at higher trophic levels, particularly in the case of web-building spiders inhabiting tropical tree communities.

Antipredator behavior of the new mass-reared unisexual strain of the Mexican Fruit Fly.

Tephritid pests controlled through the sterile insect technique (SIT) are mass-reared and subsequently released in affected areas. Several quality parameters are currently used to test adults, but none take into account interactions with a predator. When sterile males are released in the field, they will need to avoid predators until they reach sexual maturity and survive long enough to mate with wild females. Spiders are one of the most common predators that flies may encounter in release sites. In this study, we evaluated the antipredator behavior of a mass-reared sterile unisexual strain ('Tapachula-7') of the Mexican fruit fly Anastrepha ludens (Diptera: Tephritidae) against their spider predators. We sampled spiders in citrus trees to determine which families could be more common. We established the baseline activity rates of sterile Tapachula-7 (Tap-7) flies in comparison with wild flies. We also tested the behavior of the fertile and sterile bisexual strain and wild flies against hunting spiders (Family Salticidae) and orb building spiders (Family Tetragnathidae). We recorded 18 spider families, with Salticidae being the most dominant. Tap-7 flies diminished their activity in comparison with wild males at 1800 h but showed similar activity levels earlier in the day. When exposed to orb-web spiders (Leucauge venusta), Tap-7, fertile and sterile males from the bisexual strain had similar rates of survival, but Tap-7 males showed lower survival than wild males. Against hunting spiders (Phidippus audax), wild males had higher probability of defensive wing displays, but there was no difference in spider attack rates. In general, sterile Tap -7 males performed as well as males from the bisexual strain, although they had lower survival than wild males. This could be due to either mass-rearing and/or irradiation effects. We recommend the use of the defensive wing display behavior as a quality parameter and propose a rapid and effective method to evaluate fly activity. The efficiency of SIT will be improved if released sterile males have the same antipredator repertoire as their wild counterparts.

The impact of UVB radiation on the glycoprotein glue of orb-weaving spider capture thread.

Many spider orb-webs are exposed to sunlight and the potentially damaging effects of ultraviolet B (UVB) radiation. We examined the effect of UVB on the viscoelastic glycoprotein core of glue droplets deposited on the prey capture threads of these webs, hypothesizing that webs built by species that occupy sunny habitats are less susceptible to UVB damage than are webs built by species that prefer shaded forest habitats or by nocturnal species. Threads were tested shortly after being collected in the early morning and after being exposed to UVB energy equivalent to a day of summer sun and three times this amount. Droplets kept in a dark chamber allowed us to evaluate post-production changes. Droplet volume was unaffected by treatments, indicating that UVB did not damage the hygroscopic compounds in the aqueous layer that covers droplets. UVB exposure did not affect energies of droplet extension for species from exposed and partially to mostly shaded habitats (Argiope aurantia, Leucauge venusta and Verrucosa arenata). However, UVB exposure reduced the energy of droplet extension in Micrathena gracilis from shaded forests and Neoscona crucifera, which forages at night. Only in L. venusta did the energy of droplet extension increase after the dark treatment, suggesting endogenous molecular alignment. This study adds UVB irradiation to the list of factors (humidity, temperature and strain rate) known to affect the performance of spider glycoprotein glue, factors that must be more fully understood if adhesives that mimic spider glycoprotein glue are to be produced.

Optimal foraging, not biogenetic law, predicts spider orb web allometry

The biogenetic law posits that the ontogeny of an organism recapitulates the pattern of evolutionary changes. Morphological evidence has offered some support for, but also considerable evidence against, the hypothesis. However, biogenetic law in behavior remains underexplored. As physical manifestation of behavior, spider webs offer an interesting model for the study of ontogenetic behavioral changes. In orb-weaving spiders, web symmetry often gets distorted through ontogeny, and these changes have been interpreted to reflect the biogenetic law. Here, we test the biogenetic law hypothesis against the alternative, the optimal foraging hypothesis, by studying the allometry in Leucauge venusta orb webs. These webs range in inclination from vertical through tilted to horizontal; biogenetic law predicts that allometry relates to ontogenetic stage, whereas optimal foraging predicts that allometry relates to gravity. Specifically, pronounced asymmetry should only be seen in vertical webs under optimal foraging theory. We show that, through ontogeny, vertical webs in L. venusta become more asymmetrical in contrast to tilted and horizontal webs. Biogenetic law thus cannot explain L. venusta web allometry, but our results instead support optimization of foraging area in response to spider size.

Interspecific aggregation around the web of the orb spider Nephila clavipes: consequences for the web architecture of Leucauge venusta

This study describes a case of interspecific aggregation involving a spider's web and its effect on web architecture of another species of spider. On two transects of 100 m each, one with Nephila clavipes (Linnaeus 1767) webs and one without, we noted the spiders associated, or not, with N. clavipes webs, and compared the web architecture of the most commonly associated species, Leucauge venusta (Walckenaer 1842). The transect with N. clavipes contained more spiders in general than that without N. clavipes, most of which were L. venusta for both transects. The height above ground of L. venusta webs associated with N. clavipes presented a larger range of distribution, which closely mimicked that of N. clavipes webs except when the N. clavipes web was at ground level. Leucauge venusta webs were more inclined when in association with N. clavipes (49.4 ± 3.3° vs 20.4 ± 2.0°). We concluded that L. venusta clearly prefers to be associated with N. clavipes, and we discuss the possible advantages of this association.

Mass-mediated sex differences in climbing patterns support the gravity hypothesis of sexual size dimorphism

Abstract. The gravity hypothesis of sexual size dimorphism can explain the patterns of extreme sexual size dimorphism in spiders (males smaller than females) because small males climb faster and therefore may be better at reaching females that live in high habitats. Recently, the main prediction of a negative relationship between climbing speed and body size in spiders has been called into question. Here we induced males and females of the spider Leucauge venusta (Tetragnathidae) to run on vertical surfaces and found partial support for the gravity hypothesis. As predicted, males climb faster than females and we demonstrated that this effect is an indirect effect mediated by the negative relationship between body mass and climbing speed. We validate our results using simulated data showing that there is enough statistical efficiency in our data set to support our conclusions. We distinguished between direct and indirect effects (through mass) on sex differences in climbing speed by means of path analysis. Thus, we provide empirical evidence that by being smaller, males are able to climb faster than females. However, we found only a barely significant negative relationship between climbing speed and body size when only males were considered. Reasons for such results are discussed within the text.

The effects of capture spiral composition and orb-web orientation on prey interception

Cribellar prey capture threads found in primitive, horizontal orb-webs reflect more light, including ultraviolet wavelengths, than viscous threads found in more derived, vertical orb-webs. Low web visibility and vertical orientation are each thought to increase prey interception and may represent key innovations that contributed to the greater diversity of modern, araneoid orb-weaving spiders. This study compares prey interception rates of cribellate orb-webs constructed by Uloborus glomosus (Uloboridae) with viscous orb-webs constructed by Leucauge venusta (Tetragnathidae) and Micrathena gracilis (Araneidae). We placed sectors of cribellar and viscous threads side by side in frames that were oriented either horizontally or vertically. The webs of both U. glomosus and L. venusta intercepted more prey when vertically oriented. In each orientation L. venusta webs intercepted more insects than did U. glomosus. Although this is consistent with the greater visibility of cribellar threads, the more closely spaced capture spirals of L. venusta may have contributed to this difference. Micrathena gracilis webs intercepted more prey than did U. glomosus webs, although web orientation did not affect the performance of this araneoid species. The stickier and more closely spaced capture spirals of M. gracilis may have enhanced the interception rates of this species and accounted for the greater number of smaller dipterans retained in its webs. The tendency for these slow, weak flight insects to be blown into both horizontal and vertical webs may account for similar interception rates of horizontal and vertical M. gracilis webs. These observations support the enhanced prey interception of vertically oriented orb-webs, but offer only qualified support for the contributions of lower visibility viscous capture threads.

VARIATIONS IN WEB CONSTRUCTION IN LEUCAUGE VENUSTA (ARANEAE, TETRAGNATHIDAE)

Abstract The distribution of female Leucauge venusta (Walckenaer 1841) in a coffee plantation in southern Mexico was studied in order to determine the vertical distribution of this spider. Principal component analysis clearly identified the presence of three distinct groups of L. venusta webs, based on the number of spirals/web and principally on the height at which the webs were located; most L. venusta webs (63/100) were close to the ground. Spiders on high webs (153.8 ± 3.6 cm above ground, mean ± S.E.) were significantly larger and heavier than spiders on lower webs. Large spiders had significantly larger, better developed ovaries, than smaller conspecifics, presumably indicative of sexual maturity. Significantly more insects were captured by sticky traps placed at 50 cm height than in the traps placed at 150 cm height; the most numerous captures were Diptera. However, insects caught at 150 cm were significantly larger than those caught at 50 cm above ground. We concluded that as sexual development pr...

Host selection by a kleptobiotic spider

Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.

ESTIMATING THE STICKINESS OF INDIVIDUAL ADHESIVE CAPTURE THREADS IN SPIDER ORB WEBS

Sticky threads improve an orb web's ability to retain the insects that strike it, allowing a spider more time to subdue these insects before they can escape from the web. The adhesive capture threads found in most orb webs feature small droplets of aqueous material. Inside each droplet, glycoprotein granules coalesce to impart thread stickiness. An independent contrast analysis of threads produced by the adults of five species (Leucauge venusta, Argiope trifasciata, Micrathena gracilis, Cyclosa conica, Araneus marmoreus) and ontogenetic studies of the threads of two of these species show that the volume of material in a thread's droplets is directly related to its stickiness. Models based on these analyses predict thread stickiness to within an average of 11% of the mean measured values using measurements of droplet diameter and distribution that are easily made with a compound microscope. This approach will facilitate the inclusion of thread stickiness in studies that examine the properties and performance of spider orb-webs.

Host selection by a kleptoparasitic spider

Argyrodes globosus (Keyserling, 1884) is a small kleptoparasite spider that steals prey from the web of web-building spiders. In coffee plantations in the south of Mexico it was observed to parasitize five species: Gasteracantha cancriformis (Linnaeus, 1785) and Verrucosa arenata (Walckenaer, 1841) (Araneidae), Leucauge mariana (Keyserling, 1881) and Leucauge venusta (Walckenaer, 1841) (morphologically indistinguishable species) and Leucauge argyra (White, 1841) (Tetragnathidae). G. cancriformis was more frequently parasitized than the other hosts. An analysis of web diameter for each host species indicated that for L. mariana/venusta, L. argyra and V. arenata the kleptoparasite was associated with webs of a certain size range (23-33cm diameter) although a far larger range of web sizes was available (17-50cm diameter). The average size of the web of G. cancriformis (~23cm) appeared to be close to the preferred size for the kleptoparasite and this, together with an apparent absence of host aggression, may explain the prevalence of A. globosus with this host. For the parasite, web size choice may involve a tradeoff among diverse factors including prey capture rate, ease of access to the web and aggressive behaviour by the host.