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Ants are among the most ecologically dominant animals in several terrestrial ecosystems. Some myrmecophile species use ants to transport themselves, a behavior known as phoresy or phoresis. Although phoresis is commonly reported in arachnids such as pseudoscorpions or acari, it is very unusual among spiders. Phoresis on ants has only been reported in one genus of spiders, the sac-spider Attacobius Mello-Leitão, 1925 and for only two Brazilian species. In this report, we describe this amazing behavior in Attacobius nigripes (Mello-Leitão, 1942) for the first time in association with a new host, the leaf-cutting ant Acromyrmex lobicornis Emery, 1888. This record extends the geographic distribution of this spider species to the southwest of Argentina, from the Chaco into the Monte Desert region. We briefly describe the riding behavior of spiders and discuss the myrmecophile association between this species and A. lobicornis. More studies are needed to understand the evolutionary context of this association. [ABSTRACT FROM AUTHOR]

In this paper the findings of a global literature and social media survey of spider mycoses are presented. Our survey revealed that spider mycoses occur in the geographic belt between latitude 78°N and 52°S, and that more than 40 out of the known 135 spider families (ca. 30%) are attacked by fungal pathogens. Jumping spiders (Salticidae), cellar spiders (Pholcidae), and sheet-web spiders (Linyphiidae) are the families most frequently reported to be attacked by fungal pathogens (combined >40% of all reported cases). Ninety-two percent of the infections of spiders can be attributed to pathogens in the order Hypocreales (phylum Ascomycota), and almost exclusively the families Cordycipitaceae and Ophiocordycipitaceae. Within the Hypocreales, the asexually reproductive genus Gibellula is an historically species-rich and widespread genus of specific spider-pathogenic fungi. For ca. 70 species of spider-pathogenic fungi their hosts could be identified at least to family level. The data presented here reaffirm the findings of previous studies that spider-pathogenic fungi are most common and widespread in tropical and subtropical forested areas, with free-living cursorial hunters – dominated by Salticidae – being the most frequently infected. Cursorial hunters (especially Salticidae) and subterranean cellar spiders (Pholcidae) are the most frequently fungus-infected spiders in North America, whereas web-weavers (especially Linyphiidae and Pholcidae) are the most common spider hosts in Europe. Our survey implies that spider-pathogenic fungi are an important mortality factor for spiders which has hitherto been underestimated. [ABSTRACT FROM AUTHOR]

Cold temperatures can cause injury and death, and thermal tolerance influences organismal abundance, distribution, and physiology. We characterized cold tolerance and supercooling point (SCP) in the broadly distributed jumping spider Phidippus audax (Hentz, 1845). We found that P. audax is freeze-avoidant, surviving chilling but not freezing. Freeze-avoidant organisms can reduce harm by lowering their supercooling point (SCP), the temperature at which they freeze. We assayed fall/winter SCP in field-acclimated spiders from Michigan and compared lab-acclimated spiders from Texas, Oklahoma, and Michigan. Field-acclimated Michigan spiders decreased their SCP from –4.7 °C in September to –12.9 °C in November. In the lab, Michigan spiders had the lowest SCP (–7.65 °C) followed by Oklahoma (–6.21 °C) and Texas (–5.50 °C). In December and January, nearly all the spiders from Texas and Oklahoma died in the simulated freezing conditions while the Michigan spiders survived at high rates, further suggesting that the Michigan spiders were hardiest followed by Oklahoma and Texas. The lab-acclimated spiders did not consistently reduce their SCP from October to December. Smaller spiders had lower SCPs than larger spiders, and the Michigan spiders were significantly smaller than those from Texas or Oklahoma, suggesting that smaller overwintering size or delayed molting to mature size/sexual maturity may be favored by selection in colder climates. This could help explain differences in size and life cycle between northern and southern P. audax, as well as a previously described trend for smaller spiders to be more common in colder areas or Europe. [ABSTRACT FROM AUTHOR]

Argiope anasuja Thorell, 1887 is a species of orb-weaving spider found in tropical and subtropical regions of the world. Despite its widespread distribution, little is known about its natural history and mating behavior. In this study, I describe some aspects of the natural history and mating behaviors of A. anasuja in captivity and in natural habitats. The spiders were found to occupy less shady areas close to water bodies, building their webs between 50 to 200 cm above the ground level. Web decorations were common in female webs, primarily in the central area, and consisted of dense zigzag bands of silk. A significant difference in copulation duration was observed between cannibalized and non-cannibalized individuals. Furthermore, a significant difference in copulation duration was found between individuals in natural environments and laboratory conditions. However, no significant difference was observed in courtship duration between individuals in natural environment and laboratory conditions. Understanding the mating behaviors of A. anasuja is important because they play a key role in determining the success of mating. This study highlights the natural history and mating behavior of A. anasuja, contributing to our understanding of this species in Sri Lanka. [ABSTRACT FROM AUTHOR]

The spider, Myrmecicultor chihuahuensisRamírez, Grismado & Ubick 2019 is a myrmecophage. In an earlier study, we found that the spider's cuticular hydrocarbon (CHC) profile overlapped with that of its prey. In the present study, we photographed nests of Novomessor ants to determine whether these spiders live inside the ant nest with their prey or in the vicinity of the colony. We set up two 35 mm cameras over two main entrances of one nest of N. albisetosus (Mayr 1886) such that images would be captured of the ant colony surface (including the entrances) every 15 – 60 sec over five consecutive nights. These images included five showing M. chihuahuensis directly at one of the nest entrances investigating dead ants. The spider was not seen away from the entrance. This study provides evidence suggesting that this myrmecophage may live inside the colony with the ants it eats. [ABSTRACT FROM AUTHOR]

As in other Palpimanidae, two pairs of posterior spinnerets present in typical Araneomorphae are vestigial in Palpimanus uncatusKulczyński, 1909, with only the anterior lateral spinneret (ALS) pair prominent. Nevertheless, in late juvenile and adult females, spigots appear in the ancestral posterior spinneret region (PS). Consistent with these spigots serving cylindrical silk glands, females construct substantial egg sacs. While juveniles and adults exhibit a compressed PS, in postembryos it is fully extended. Piriform silk gland (PI) spigots form a linear array on ALSs from the 1st stadium, increasing in number during ontogeny by addition of PIs of the tartipore-accommodated (T-A) subtype (i.e., functional during proecdyses). The number of T-A PIs added from one stadium to the next and locations occupied by their spigots often exhibit a stereotypic pattern, especially consistent in early instars. The number of non-T-A PIs remains constant through ontogeny from the 1st stadium: one per ALS rather than the two per ALS inferred in a few araneoids. The secondary major ampullate silk gland (2° MaA) spigot, primitively uni-shafted among araneomorphs, has become modified into a multi-shafted spigot with extended base, the number of shafts increasing during ontogeny. However, the multiple ducts that connect to the shafts continue to be accommodated during proecdysis by a single enormous tartipore. Sexual dimorphism is present, with late stadium females having greater numbers of T-A PI spigots and 2° MaA spigot shafts. Observations are presented pertaining to feeding behavior, sexual cannibalism (absent), habitat, winter diapause, numbers of molts, and longevity. [ABSTRACT FROM AUTHOR]

Globally, arthropod populations are declining at alarming rates, but the causes are rarely understood. Our research details and examines possible causes for fluctuations in the size of a Costa Rican population of golden silk orbweaver spiders (Trichonephila clavipes (Linnaeus, 1767)). Over a seven-year period from 2013–2019, we noted a sharp decline and then partial recovery of the study population during the wet season (June, July), but then failed to locate any spiders during a brief survey in June 2022 when they would otherwise be abundant. We monitored webs daily during 2013–2019 to test whether variation in prey capture, competitors, female size, male availability, predation, temperature, or rainfall related to population fluctuations. We were unable to explain T. clavipes population trends with the collected data. Future studies are needed to determine whether the extremely low population densities we witnessed in 2017 and 2022 can be interpreted as the lowest values of this species' normal population fluctuation cycle or whether these extremes are part of a long-term spider decline. [ABSTRACT FROM AUTHOR]

Taxonomic studies have evolved greatly since their early stages and new techniques have been incorporated to improve species descriptions. Those involving the comparison of traits, either quantitatively or qualitatively, can be difficult because the identification of a species must rely on the experience of the observer and errors can occur when cryptic species are involved. Molecular methods have been used to fill these gaps, but morphological methods are still needed to match the recognized molecular species with an adequate taxonomic description. Focusing on the trapdoor spider genus ProshermachaSimon, 1908, we provide a case study using Geometric Morphometrics (GM) techniques to identify morphological divergence between species found in the south-western Australia region. We used GM to identify morphological divergence from museum-preserved specimens by examining shape variation of sexual characters from 39 male specimens from five different localities on a single mountain range. Variation in the shape of both the palpal bulb and tibia provided strong evidence to distinguish two morphotypes, while metatarsus shape showed fewer between-locality differences. Our results illustrate the utility of GM methods, when applied to a few taxonomically-informative structures, as a quantitative species delimitation tool for taxonomic studies. [ABSTRACT FROM AUTHOR]

Jumping spiders (Araneae: Salticidae) possess a visual system that is exceptional among arthropods, mainly due to its unmatched acuity. Although vision of these spiders has been studied for decades, some of its main aspects remain unclear. One such aspect is the light spectrum visible to salticids, which is surprisingly heterogenous and involves various underlying physiological mechanisms. The results of the behavioral experiments with the regal jumping spider (Phidippus regius) presented in this study provide evidence that these vision-dependent spiders are able to capture their prey even under red (longwave) light, which is usually not perceived by spiders. Broader use of this experimental design in studies of spider vision is discussed. [ABSTRACT FROM AUTHOR]

Eleven new species from the Scytodoidea group are described from mainland Ecuador: in the family Drymusidae, Drymusa pristirana sp. nov. (female) and in the family Scytodidae, Scytodes amazonica sp. nov. (male, female); S. argelia sp. nov. (female), S. ayampe sp. nov. (female), S. choco sp. nov. (male, female), S. costa sp. nov. (female), S. jaguar sp. nov. (male), S. loja sp. nov. (female), S. minus sp. nov. (male); S. orellana sp. nov. (male, female); and S. tayos sp. nov. (male). The new species D. pristirana sp. nov. presents a unique morphological character on the ventral surface of the female abdomen. The type specimens of S. lineatipesTaczanowski, 1874 from French Guiana and S. luteola Simon, 1893 from Venezuela are imaged for the first time, and S. romitii Caporiacco, 1947 is removed from synonymy with S. lineatipes. [ABSTRACT FROM AUTHOR]

The open-holed trapdoor spiders of the Teyl damsonoides-group (formerly included in the now synonymized genus MerrediniaMain, 1983) are revised, and 20 new species are described from the biodiversity hotspot of south-western Western Australia. The only previously described species, T. damsonoides (Main, 1983), is further re-described and re-illustrated, and molecular data from seven genes for a subset of nine species are analyzed using Bayesian methods. The damsonoides-group of Teyl are unusual for their stunning bi-colored appearance and the bowed morphology of the male metatarsus I, and we here document the known diversity and biology of these little-known spiders. [ABSTRACT FROM AUTHOR]

Organisms can optimize their reproductive success by differential resource allocation. When adult survival is low, investment of all resources into a single reproductive event can be beneficial, favouring a semelparous strategy. In the spider genus Stegodyphus Simon, 1873 (Eresidae), all species are considered semelparous, based on observations of ancestral subsocial species. However, derived social species show task differentiation and helping by non-reproducing females. This could facilitate a facultative iteroparous strategy by providing sufficient resources to meet the threshold for repeated reproduction. We investigated the reproductive behaviour of groups with single breeding females in the cooperative breeding Stegodyphus dumicola Pocock, 1898. We found that mothers can depart from a strictly semelparous lifestyle by producing more than one clutch. The facultative iteroparity in S. dumicola may enhance colony growth and survival, and act as a mechanism to maintain sociality. [ABSTRACT FROM AUTHOR]

Most spiders are exclusively terrestrial with only some groups venturing into aquatic habitats, and only a handful of representatives colonizing the marine intertidal zone. Here, we describe a new intertidal trapdoor spider species, Idioctis parilarilao sp. nov., from southern Taiwan and Green Island (Lutao). The original DNA barcode enables species delimitation between different populations from Taiwan and the morphologically closest species, Idioctis xmas, from Christmas Island, Indian Ocean. These analyses reveal that all populations from Taiwan, including Green Island, are conspecific, and are distinct from Idioctis xmas. Given the lack of representation of other species in public databases, our COI gene tree should be seen as preliminary, but it does support the monophyly of the genus Idioctis. As the genus was not previously known from East Asia, our discovery vastly extends the distribution range of Idioctis and the family Barychelidae. Given the tectonic and volcanic specifics of the history of Taiwan and Green Island, and the direction of the known oceanic currents, we provide a preliminary explanation of the biogeographic and diversification history of intertidal spiders in the region. [ABSTRACT FROM AUTHOR]

In this study, I provide the first description of mating behavior in the field for the genus Castianeira Keyserling, 1879 (Araneae: Corinnidae). Females have been observed building intricate mounds over their egg sacs; this study describes mating behavior while the female was building a mound--suggesting that females may have more than one clutch of offspring during the mating season or that she may store sperm for the next mating season. Analysis of my field footage and observational data revealed a simple mating behavior with little pre-or post-copulatory interaction. I compared my observations with laboratory observations by Montgomery (1909) of Castianeira descripta (Hentz, 1847) and Castianeira longipalpa (Hentz, 1847). The mating behaviors are similar in length but the sequence and duration of coupling differed. These observations create a starting point for better researching courtship and mating behavior of this spider, the number of egg sacs produced during a season, as well as the role of mound-making in the reproduction process. [ABSTRACT FROM AUTHOR]

Specialists possess specialized trophic adaptations. Spiders of the genus Palpimanus Dufour, 1820 are araneophagous spiders which also catch alternative prey. They have morphological, behavioral, and venomic adaptations tuned to higher efficacy in the capture and processing of other spiders. Here, we tested the hypothesis whether Palpimanus can develop on two prey types. We reared spiderlings of Palpimanus spp. on a diet composed of spiders and of insects, and recorded their performance. We found that Palpimanus exhibited significantly higher mortality on the insect diet. In fact, only spiderlings on the spider diet were able to develop. The developmental rate was slow, as one instar lasted on average more than 60 days. On the basis of this finding, we estimated that the life cycle is at least biennial. We conclude that Palpimanus spiders possess specialized prey-capture adaptations towards spider prey which prevent them to utilize alternative prey. [ABSTRACT FROM AUTHOR]

Most spiders are exclusively terrestrial with only some groups venturing into aquatic habitats, and only a handful of representatives colonizing the marine intertidal zone. Here, we describe a new intertidal trapdoor spider species, Idioctis parilarilao sp. nov., from southern Taiwan and Green Island (Lutao). The original DNA barcode enables species delimitation between different populations from Taiwan and the morphologically closest species, Idioctis xmas, from Christmas Island, Indian Ocean. These analyses reveal that all populations from Taiwan, including Green Island, are conspecific, and are distinct from Idioctis xmas. Given the lack of representation of other species in public databases, our COI gene tree should be seen as preliminary, but it does support the monophyly of the genus Idioctis. As the genus was not previously known from East Asia, our discovery vastly extends the distribution range of Idioctis and the family Barychelidae. Given the tectonic and volcanic specifics of the history of Taiwan and Green Island, and the direction of the known oceanic currents, we provide a preliminary explanation of the biogeographic and diversification history of intertidal spiders in the region. [ABSTRACT FROM AUTHOR]

Animals use nests for various functions including laying eggs, raising young and gaining protection from predators. Social insect colonies provide rich microhabitats for various foreign inhabitants. Social spiders in the family Eresidae live in large, long-lasting colonies with a dense silken nest where spiders reside in complex capture webs. Social spider colonies contain several organisms apart from the host spiders, yet little is known about the foreign species and their roles. In this study, we cataloged foreign animals found in the nests and webs of the Indian social spider Stegodyphus sarasinorum Karsch, 1892 from different sites in India. We then examined the abundance and diversity of foreign spiders in adult and juvenile colonies, and the nature of interaction of foreign spiders with host S. sarasinorum spiders. We found spiders classified into nine families and insects classified into five orders and a few small vertebrate taxa associated with S. sarasinorum colonies. Adult S. sarasinorum nests and webs contained significantly more foreign spiders than juvenile colonies. However, diversity of foreign spiders did not increase with the number of host spiders. Additionally, we found that foreign spiders found inside the nests preyed on individual S. sarasinorum spiders. Our study sheds light onto the intriguing biology of nest- and web-associates of social spiders. [ABSTRACT FROM AUTHOR]

A new species of giant trapdoor spider, Euoplos dignitas sp. nov. (family Idiopidae), is described from the Brigalow Belt of inland Queensland, Australia. Phylogenetic analysis of a six gene molecular dataset for the tribe Euoplini reveals that this species is sister to the spinnipes-group from eastern Queensland, and unrelated to a morphologically similar congener (E. grandis Wilson & Rix, 2019) that occurs further south in the Brigalow Belt. Both E. dignitas sp. nov. and E. grandis are very large, scopulate, plug door-building trapdoor spiders from transitional woodland habitats on vertosols ('black soils'), with superficially similar females and strongly sexually-dimorphic 'honey-red' males. Information on the known biology and distribution of E. dignitas sp. nov. is summarized, and a conservation assessment is provided under the International Union for Conservation of Nature's (IUCN) Red List Criteria, indicating that this species is likely Endangered. [ABSTRACT FROM AUTHOR]

Spiders are usually found through all seasons in the subtropics, but little is known about their seasonality patterns and how they respond to abiotic factors, especially in species-rich regions such as Brazil. We investigated the seasonal variation in spider communities and the possible influence of abiotic factors (e.g., temperature, rainfall) on spider abundance, species richness and composition in subtropical riparian forest in four river basins. Changes in spider abundance among seasons differed between ontogenetic stages: there were more spiderlings in the autumn, and similar numbers of adults year round. Species richness, on the other hand, was highest in spring and summer. Species composition differed between seasons and river basins. Several factors may be behind diversity changes in the araneofauna among seasons, however, none of the abiotic factors evaluated showed a strong direct influence. Seasonal patterns varied, with different species having peaks in all three seasons but autumn. Seasonality is clear in these spider communities but not all patterns follow predictions from simple temperature changes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Patterns of phototaxis are incompletely characterized in arachnids and hardly generalizable because of large variations in orders, families, species, environments, and methods employed. In a neotropical forest of French Guiana, we tested the effect of both light and diameter on pitfall trap catches. Light had a significant effect on capture rates of all arachnids and on Araneae alone, with more individuals caught in lit traps. Without light, pitfall diameter had no effect on capture rates, while in lit traps, significantly fewer individuals were captured only in smaller traps. Light trapping is thus a promising tool to complete inventories in tropical forests. This field experiment calls for further studies of the mechanisms by which arachnids are attracted by light, especially by unraveling an actual phototaxis from indirect effects like prey attraction. [ABSTRACT FROM AUTHOR]

"Primary" webs of uloborids have large numbers of very fine lines and usually lack sticky cribellum silk. This paper reviews their taxonomic distribution (19 species in 5 genera) and the ontogenetic stages in which primary webs are built (spiderlings newly emerged from the egg sac, older juveniles, mature males, and normal and senile females), expands the knowledge of construction behavior, and describes several previously unnoticed design details. Primary webs differ from typical uloborid orbs in several ways: large numbers of fine radial and non-radial lines; facultative hub removal and replacement; usually closely spaced temporary spiral loops; and lines beyond the frame lines. Construction of supplemental radii in primary webs is distinctive in several respects: break and reel construction; tendencies to lay successive radii either on opposite sides of the web or close together in the same sector; high frequencies of aborted trips from the hub to the frame; production of multiple lines during a single trip from the hub to the frame and back; long pauses during the production of single radii; and variation in the sequences in which radial lines are added to a given sector. Some aspects of primary web construction resemble araneoid rather than typical uloborid behavior. The relation between primary webs and the evolution of orb webs, and the mechanism that spiders use to produce abundant non-radial lines despite making only radial movements during web construction remain uncertain. We speculate that primary webs are favored when spiders are unable to afford the costs of producing cribellate silk for a typical orb. [ABSTRACT FROM AUTHOR]

We describe two new Nesticus Thorell, 1869 from Walker County, Georgia, USA. Nesticus lula sp. nov. is known from two caves on the eastern edge of Lookout Mountain and N. cressleri sp. nov. is known from three caves on Pigeon Mountain. Morphological and molecular evidence indicates the distinctiveness of both species when compared to other Nesticus from the southern Appalachians. Nesticus lula has reduced eyes and N. cressleri is eyeless. Both species are of conservation concern, as they are known from only a handful of sites spanning extremely limited ranges. This work contributes to our understanding of cave biodiversity in Georgia and of the Nesticus radiation in the southern Appalachians. [ABSTRACT FROM AUTHOR]

Spiders play a key role in forest food webs, where they regulate decomposer populations and may act as predators of pests and disease vectors. Spider community composition is determined in part by vegetation structure. Therefore, the exclusion of large mammals, such as deer and wild boar, through wildlife fencing may affect the composition of spider communities and their prey in forest ecosystems. Web-building spiders and their prey were hand-collected in plots that had been fenced for three years, as well as adjacent unfenced plots in a mixed temperate forest in north-eastern Germany. Additionally, spiders in the leaf litter were sampled in fenced and unfenced subareas by sieving litter. Wildlife fencing did not significantly affect spider densities or community composition per microhabitat. However, fencing affected the cover of different microhabitats significantly as there was a higher density of larger trees and higher leaflitter cover in fenced plots while there was a higher percentage of bare ground and deadwood in unfenced plots. Spider communities and their prey composition differed significantly between microhabitats (deciduous trees, coniferous trees, dead wood, understory vegetation, leaf litter) independent of fencing. Thysanoptera prey was mainly caught by spiders on coniferous trees and in the understory vegetation. Heteroptera prey were captured most frequently in the understory vegetation while Hymenoptera (excl. Formicidae) prey were mostly caught on deciduous trees. Several spider species showed a preference between deciduous and coniferous trees in the mixed forest. Wildlife fencing alters the vegetation structure of mixed forests and has indirect effects on spider communities and their role in forest food webs due to alteration of microhabitat availability. [ABSTRACT FROM AUTHOR]

Two new species of pelican spiders (family Archaeidae) are described from rainforest habitats in south-eastern Queensland, Australia – Austrarchaea davidi Rix, sp. nov. and A. laidlawae Rix, sp. nov. – and the female of A. clyneaeRix & Harvey, 2011 is described for the first time. Phylogenetic analysis of a mitochondrial molecular dataset for the genes cytochrome c oxidase subunits I and II reveals that these two new species are the closest relatives of A. judyaeRix & Harvey, 2011 and A. clyneae, respectively, with mitochondrial sequencing also used to identify newly-collected specimens of Austrarchaea from populations throughout south-eastern Queensland. These recent collections were largely made during dedicated survey work conducted after the devastating 2019–20 summer bushfires in eastern Australia. We further provide a synopsis of the archaeid fauna of south-eastern Queensland, which is comprised of 11 species in two monophyletic regional-endemic clades. A revised key to species is presented for both clades, along with updated distributional information, and live habitus images for nine of the 11 species. [ABSTRACT FROM AUTHOR]

The spider Myrmecicultor chihuahuensis Ramírez, Grismado & Ubick (Myrmecicultoridae) was described in 2019 and hypothesized to be a myrmecophile, living inside the nests of Novomessor (Myrmicinae) and perhaps also Pogonomyrmex (Myrmicinae) ants. To test the hypothesis that M. chihuahuensis are chemical mimics of their host ants, we carried out behavioral bioassays to observe interactions between the spiders and the host ants. We compared the cuticular hydrocarbon (CHC) profiles of the spiders and the ants. We discovered that this new species of spider is a myrmecophage, displaying hunting strategies similar to other myrmecophagous spiders, particularly those in the genus Zodarion Walckenaer, 1826 (Zodariidae). The CHC profile of M. chihuahuensis did not match the profile of the ants with which it associates, Novomessor albisetosus (Mayr), but ants and spider shared several compounds, potentially involved in species recognition. [ABSTRACT FROM AUTHOR]

Sociality in spiders has evolved independently multiple times, resulting in convergently evolved cooperative breeding and prey capture. In all social spiders, prey is captured by only a subset of group members and then shared with other, non-attacking group members. However, spiders' propensity to attack prey may differ among species due to species-specific trade-offs between risks, costs and benefits of prey capture involvement. We explored whether engagement in prey attack differs among three social Stegodyphus species, using orthopteran prey, and found substantial differences. Stegodyphus mimosarum Pavesi, 1883 had a low prey acceptance rate, was slow to attack prey, and engaged very few spiders in prey attack. In S. sarasinorum Karsch, 1892, prey acceptance was high, independently of prey size, but more spiders attacked when prey was small. While medium-sized prey had higher acceptance rate in S. dumicola Pocock, 1898, indicating a preference, the number of attackers was not affected by prey size. Our results suggest that the three species may have different cooperative prey capture strategies. In S. mimosarum and S. dumicola, whose geographical ranges overlap, these strategies may represent niche specialization, depending on whether their respective cautious and choosy approaches extend to other prey types than orthopterans, while S. sarasinorum may have a more opportunistic approach. We discuss factors that can affect social spiders' foraging strategy, such as prey availability, predation pressure, and efficiency of the communal web to ensnare prey. Future studies are required to investigate to which extent species-specific cooperative foraging strategies are shaped by ontogeny, group size, and plastic responses to environmental factors. [ABSTRACT FROM AUTHOR]

The World Arachnida Catalog (WAC, online at https://wac.nmbe.ch) is introduced as an amalgamation of the highly successful World Spider Catalog (WSC), the Pseudoscorpions of the World Catalog, and the Smaller Arachnid Order Catalogs. The new catalogs present all available taxonomic information on eight arachnid orders (Amblypygi, Araneae, Pseudoscorpiones, Ricinulei, Palpigradi, Schizomida, Solifugae and Uropygi) in a single location and a standardized format, continuously updated by specialists, to members of the World Spider Catalog Association (WSCA). For the first time, the majority of taxonomic literature for Pseudoscorpiones and the smaller arachnid orders will be available in downloadable PDF format for members according to the Swiss copyright laws. Up-to-date counts of families, genera and species are given alongside the current taxonomy for each taxon. Now in a common place and presented in an almost unified format, the new catalog aims to become the primary repository of taxonomic information for the Arachnida and will hopefully stimulate arachnological research across all arachnid orders by removing boundaries imposed by literature accessibility, incompatibility of formats, or taxonomic jargon. [ABSTRACT FROM AUTHOR]

Sexual cannibalism is common in many species of arachnids. Studies investigating Dolomedes tenebrosus Hentz, 1844, have even discovered the occurrence of obligatory male self-sacrifice during copulation. In this system, females subsequently cannibalize males, and this cannibalism leads to higher fitness for both partners. Unfortunately, our understanding of the evolution of such an extreme mating system is challenged by the absence of information for close relatives. To that end, this study explores the courtship behavior, mating system and cannibalism dynamics of the spider Dolomedes scriptus Hentz, 1845. To determine whether female and male D. scriptus mate multiply, we recorded interactions of repeatedly exposed focal females and focal males to new mating partners for three days. We also quantified attacks and cannibalism events that occurred both before and after every copulation. We found male D. scriptus court females by waving their forelegs during their approach and tapping the females prior to mounting. In our remating trials, none of the female D. scriptus accepted additional males after their first mating over the three-day period. In contrast, male D. scriptus were polygynous, often mating with multiple females. Across the trials, sexual size dimorphism was a predictor of whether mating occurred, with similarly sized pairs being more likely to mate. Additionally, previously mated females were less likely to cannibalize males--an unusual pattern for spiders. Like other species of Dolomedes Latreille, 1804, our results suggest a strong role of female aggression in D. scriptus mating system dynamics. [ABSTRACT FROM AUTHOR]

The ichneumonid parasitoid Sinarachna nigricornis (Holmgren, 1860) was associated only with Araneus sturmi (Hahn, 1831) in the studied locality. The normal capturing orb web of A. sturmi was always vertical and had a median of 18 radii and 9 spirals in laboratory conditions. When spiders did not build capture webs, they built resting and molting webs which consisted of a few threads between the ends of the provided tree twigs. There were no significant differences in the number of radials and spirals between unparasitized spiders and spiders parasitized by early instar parasitoid larvae. Araneus sturmi under manipulation by S. nigricornis built a modified cocoon web, serving parasitoid larva pupation. S. nigricornis exhibited high plasticity in the architecture of the cocoon web induced by its penultimate instar larva. The most common cocoon web was of 3D architecture with a small central silk platform, from which the wasp cocoon was suspended by its apical end (72% of webs). In 22% of cases, the cocoon web consisted only of a few threads, presumably resembling a molting web. In one case, the manipulated spider built a 3D tangle, though radials and the central hub (typical for the normal capturing web) were also present. The genus specificity of the cocoon web architecture described here, in which the typical cocoon web exhibits a sparse but strong 3D architecture and in which the wasp cocoon is suspended by its apical end at the center, is expected for the genus Sinarachna. [ABSTRACT FROM AUTHOR]

There are few works on the reproductive behavior of species of cribellate spiders. Even more scarce are studies of the reproductive behavior of representatives of the Desidae, such as the genus Metaltella Mello-Leitão, 1931. In this paper, we describe for the first time the reproductive behavior of Metaltella iheringi (Keyserling, 1891), a species that is characterized by complex genitalia in both sexes. We determined frequencies and durations of the behaviors in the different phases. Thirty virgin males were exposed to virgin females and the behaviors performed by each sex, as well as their frequencies, were recorded. Three phases were identified: pre-copulatory, copulatory, and post-copulatory. The most frequent behaviors were chelicera-palp rubbing, abdomen vibration and web-stretching by the male, and body-shaking and leg-tapping on the web by the female. When the male grabbed the female, she typically fell into a state of quiescence (the female remained motionless with legs in a semi-flexed position) and she remained so even after the male ended the copulation. Mating was characterized by low aggression by the female and a low incidence of cannibalism. In the post-copulatory phase, the male performed frequent behaviors such as abdomen vibration, sperm induction, and post-copulatory cohabitation. We discuss the possible implications of these behaviors in a pre- and post-copulatory sexual selection context. We also provide information that serves as a basis for future studies to understand the mechanisms involved in these behaviors. [ABSTRACT FROM AUTHOR]

The pholcid spiders Modisimus bribri Huber, 1998 and M. guatuso Huber, 1998 construct three-dimensional webs, including sheet dome and irregular shapes, occasionally shared by males and females. We studied species spatial disaggregation and confirmed web-sharing and prey capture dominance in shared webs. We observed 22 M. bribri and 25 M. guatuso webs and recorded their height above the ground, dome dimensions, and web-sharing. In shared webs, we recorded which individual captured prey. Modisimus bribri builds webs at greater heights (~6.5 times), with larger dimensions (~2 times) than M. guatuso. In both species, neither the occupant sex nor the number of individuals on the web had a significant effect on web dimensions. We confirmed differential web location between species and did not find evidence of chivalrous dominance in prey-capture in shared webs. This study contributes to the general knowledge of three-dimensional web-building spiders, posing new questions for future research. [ABSTRACT FROM AUTHOR]

We studied dispersal of brown recluse spiders, Loxosceles reclusa (Gertsch & Mulaik, 1940), around an infested urban garage using pitfall traps. Over a four-month period, 23 were captured from a source population that averaged 100 individuals observed in nocturnal censuses. Loxosceles reclusa were captured in far lower proportions compared to their potential source population size than were other spiders such as theridiids and agelenids that also resided in the garage, albeit in far lower numbers. Dispersal was weakly positively correlated with the source population size. We compare our findings to anecdotal reports from prior studies and the general consensus that brown recluse spiders are poor dispersers to argue for more detailed examination of the movement and specific habitat requirements of this medically important spider. Habitat specificity and high mortality during dispersal may help explain the highly clustered spatial distribution of brown recluse spiders, not only a lack of attempted emigration. [ABSTRACT FROM AUTHOR]

The Araneidae is among the most speciose spider families, but there are few karyotype studies (1.9%) and some species-rich clades are without any chromosomal study. Understanding the evolution of chromosome number and Sex Chromosome Systems is made more difficult by many uncertain evolutionary relationships within the family. In this work, the chromosomal analysis of eight araneid species (Acacesia benigna Glueck, 1994, Actinosoma pentacanthum (Walckenaer, 1841), Alpaida bicornuta (Taczanowski, 1878), Dubiepeira Levi, 1991 sp., Gasteracantha cancriformis (Linnaeus, 1758), Parawixia bistriata (Rengger, 1836), Verrucosa meridionalis (Keyserling, 1892) and Verrucosa scapofracta Lise, Kesster & Silva, 2015), contribute to discussions of some evolutionary scenarios of chromosome evolution. The gonads were submitted to colchicine treatment, hypotonization, slide preparation, and Giemsa staining. The species analyzed showed 2n♂ = 24 (11II + X1X2), except Dubiepeira sp. with 2n♂ = 41 (19II + X1X2X3), and both Verrucosa species, which presented 2n♂ = 47 (22II + X1X2X3) in V. meridionalis and 2n♂ = 50 (23II + X1X2X3X4) in V. scapofracta. The species analyzed possess all chromosomes with acro/telocentric chromosomal morphology. The 2n♂ = 24, X1X2 found in most species studied here is the most frequent karyotype in the Araneidae. This study presents the first chromosomal data for the diverse clade "Micrathenines", the highest diploid number among entelegynes (2n♂ = 50), and the first record of an X1X2X3X4 in the Araneidae. The chromosome data suggest a series of fission events in the origin of Verrucosa karyotypes, and a close relationship between Dubiepeira sp. and Araneus ventricosus (L. Koch, 1878). Moreover, Alpaida bicornuta can be cytotaxonomically distinguished of other Alpaida species karyotyped up to now. [ABSTRACT FROM AUTHOR]

In this work we describe Ctenus igatu sp. nov., the first ctenid spider from South America with conspicuous troglomorphic traits, including elongated appendages, reduction of eyes, and body depigmentation. The new species is only known to occur in a unique sandstone cave from the state of Bahia, north-eastern Brazil. The morphology of the genitalia suggests that Ctenus igatu sp. nov. is closely related to Ctenus fasciatus Mello-Leitão, 1943, a facultative subterranean species from caves in the state of São Paulo, south-eastern Brazil. In addition, we compared morphological traits possibly related to the isolation in subterranean habitats, such as ratios between carapace length vs. leg IV length and eye diameters vs. carapace length, of 19 species of Ctenus (17 epigean species, C. fasciatus and the new troglobitic species described herein). Our analysis showed that both C. fasciatus as C. igatu sp. nov. have morphological troglomorphisms, with C. igatu sp. nov. showing marked specializations to subterranean life. [ABSTRACT FROM AUTHOR]

Spiders in the genus Argiope Audouin, 1826 often include silken structures in their webs called decorations. Here, I report on the form and frequency of the vertical or linear decorations built by A. protensa L. Koch, 1872 as based on a survey of online digital imagery. Of 124 webs in 262 images clearly showing the web, 38.7% were decorated, less than for other congeners also sampled across their geographic range. The spider lays silk strips centered above and/or below the web’s hub; however, one web appeared to have four strips arranged in a cruciate pattern. Unlike other Argiope whose decorations consist of zigzagging bands, A. protensa weaves a derived cottony decoration of jagged strips reminiscent of those in Uloboridae. Large and geographically broad surveys of spider behavior and web structure are possible using online databases of natural-history observations. [ABSTRACT FROM AUTHOR]

Observations of spiders’ pre-dispersal behavior can be used to answer various ecological and evolutionary questions. So far, dispersal experiments have often used air currents as a stimulating factor. Effects of electric fields on the pre-dispersal behavior of spiders have recently been discovered. Electric fields may lead to unexplained variation in results and limit comparability between previous studies. Here we aim to disentangle the roles of wind and electric fields on the passive aerial dispersal of three linyphiid spider species. Our results confirm that strong electric fields in the air elicit predispersal behavior, and in combination with a light wind, facilitate dispersal (take-off). Nevertheless, even the strong electric fields employed here played a rather supplementary role in spiders’ dispersal with wind remaining the most influential factor. We recommend that studies of passive aerial dispersal should control for electric field strength but otherwise use wind as the primary stimulating factor. [ABSTRACT FROM AUTHOR]

The large size and slow movements of mature female Trichonephila clavipes (Linnaeus, 1767) permit observations of some seldom-studied details of behavioral processes, such as cutting and initiating silk lines, that help clarify functional morphology. Silk lines were cut after being grasped by the cheliceral fangs; but direct observation and details of cheliceral morphology showed that cutting was not accomplished mechanically, as has sometimes been assumed. Lines were probably cut by contact with an enzyme in the mouth region. Initiation of wrapping lines involved rapid, coordinated movements of the spinnerets and the abdomen that caused the spigots for these lines to brush against each other and dragline silk. The posterior lateral spinnerets were spread widely during wrapping; this behavior and the positions of spigots on the spinnerets probably serve to widen the swath of wrapping lines applied to the prey. [ABSTRACT FROM AUTHOR]

Badumna longinqua (L. Koch, 1867) (Araneae: Desidae) is a web-building spider indigenous to eastern and southern Australia; it has been introduced to several countries in North and South America, as well as New Zealand, Japan and Germany. In South Africa, where it was formally recorded for the first time a decade ago, B. longinqua has been sampled from the southern coastal areas (Eastern and Western Cape provinces) and central Free State Province, with almost all of the records associated with synanthropic urban habitats. We present a brief account of its invasion history in the country. Predictive ecological niche models suggest that only the southern coastal areas represent suitable habitat. This suggests that samples from the Free State (only in horticultural nurseries) can be attributed to regular translocations from the southern coastal areas, but that an unsuitable climate there prevents long-term establishment. Future climate change may further restrict this species, which prefers year-round warm, humid areas with low seasonal variability, climatic conditions that are predicted to become increasingly rare in South Africa. [ABSTRACT FROM AUTHOR]

Spiders exhibit various egg sac construction behaviors using camouflage to protect the eggs from predators and parasitoids and also perform parental care to increase offspring survival. In this study, we describe the egg sac construction behavior of Deinopis cf. cylindracea, and the camouflage characteristics of egg sac when left without the female’s active protection. Our observations showed that D. cf. cylindracea builds a fairly compact egg sac, with an outermost layer composed of dense silk. This outermost layer is dark brown, perhaps to camouflage with the substrate on which the egg sac is deposited. Moreover, females tend to hide their egg sacs with dry leaves in the litter. In addition, the overall color, shape, and size of the egg sac resemble the dry seeds of Plinia cauliflora, the plant on which D. cf. cylindracea was found. Two female spiders were positioned on their egg sacs; however, whether this behavior reflects maternal care remains unknown. Therefore, the overall egg sac construction behavior of D. cf. cylindracea may be related to a strategy for increasing fitness. This is the first behavioral record for a South American deinopid species. [ABSTRACT FROM AUTHOR]

Parasites are some of the most abundant, diverse, and ecologically important organisms on the planet. Similarly, spiders are diverse, abundant, and play important roles in many terrestrial ecosystems. It is unfortunate that our understanding of the parasites that affect spiders is so underdeveloped relative to similar fields (e.g., parasites of insects). With this review, we describe characteristics of the major groups known to parasitize spiders and illustrate the ways in which spider biology presents unique challenges and opportunities for their parasites. Particularly promising avenues of future research include testing how parasites alter their spider hosts’ behavior and ecology through density-dependent and trait-mediated effects. We close by providing future directions and testable hypotheses at the forefront of spider-parasite research. [ABSTRACT FROM AUTHOR]

Spiders exhibit various egg sac construction behaviors using camouflage to protect the eggs from predators and parasitoids and also perform parental care to increase offspring survival. In this study, we describe the egg sac construction behavior of Deinopis cf. cylindracea, and the camouflage characteristics of egg sac when left without the female's active protection. Our observations showed that D. cf. cylindracea builds a fairly compact egg sac, with an outermost layer composed of dense silk. This outermost layer is dark brown, perhaps to camouflage with the substrate on which the egg sac is deposited. Moreover, females tend to hide their egg sacs with dry leaves in the litter. In addition, the overall color, shape, and size of the egg sac resemble the dry seeds of Plinia cauliflora, the plant on which D. cf. cylindracea was found. Two female spiders were positioned on their egg sacs; however, whether this behavior reflects maternal care remains unknown. Therefore, the overall egg sac construction behavior of D. cf. cylindracea may be related to a strategy for increasing fitness. This is the first behavioral record for a South American deinopid species. [ABSTRACT FROM AUTHOR]

Accumulated studies have revealed that spiders, which are believed to be true predators, also feed on various plant materials such as pollen, nectar, and stigmatic exudate. Hereby, we report observational cases of fermented tree sap feeding by four spider species, namely Sinopoda forcipata (Karsch, 1881) (Sparassidae), Otacilia komurai (Yaginuma, 1952) (Phrurolithidae), Weintrauboa contortipes (Karsch, 1881) (Pimoidae), and Doenitzius cf. peniculus Oi, 1960 (Linyphiidae), in deciduous forests in Japan. This is the first report of spiders feeding on fermented sap, and also the first report of plant material consumption in the families Sparassidae, Phrurolithidae, and Pimoidae. [ABSTRACT FROM AUTHOR]

Studies of web evolution in spiders generally focus on the overall designs of webs in the field. As has been typical for dictynids and several other cribellate families with "irregular" webs, this study detected few discernable patterns in the field regarding the spatial organization of the highly variable, three-dimensional and largely aerial webs of the dictynid Dictyna meditata Gertsch, 1936. Nevertheless, there were three consistent sub-unit designs in the additions that spiders made to their webs in captivity, and in webs that they built from scratch in captivity: "silk ladders", with a cribellum line that zig-zagged between a pair of approximately parallel non-sticky lines; "twig ladders", with a cribellum line that zig-zagged between a non-sticky line and the substrate; and long non-sticky lines that each supported a long, slightly looped cribellum line. I suggest, using examples from dictynids and other families with long-lived, geometrically irregular webs, that this pattern of using consistent behavior patterns to add geometrically regular "modules", is widespread and ancient, but has often been missed due to damage and additions to webs in the field, and to lack of direct behavioral observations. Recent attempts to link web evolution to studies of spider phylogeny could benefit from a change of emphasis, focusing on the additions that spiders make to their webs, rather than on the currently common but necessarily vague characterizations of overall web designs seen in the field. [ABSTRACT FROM AUTHOR]

Amblypygi is a small order of arachnids that includes the whip spiders. Like other members of the clade Pedipalpi, these arachnids are cryptic predators that use their antenniform appendages to detect prey, and spinose pedipalps for quick prey capture. To date, there is very little information on the composition of their exoskeleton despite its importance in predation and defense. Here, we performed the first analysis of a whip spider exoskeleton using energy-dispersive X-ray spectroscopy (SEM-EDS). Our studies of Phrynus marginemaculatus CL Koch, 1840 were designed to (1) determine if elemental profiles differ between instars and (2) determine if and how elemental profiles of whip spiders differ from other closely related arachnids. We found the whip spider exoskeleton to contain several trace metal elements including calcium, magnesium, manganese, potassium, sodium, and zinc. The diversity and abundance of trace elements is relatively low throughout the exoskeleton of 2nd instars but increases in adults. In particular, the chelicerae and pedipalps are well reinforced with several metal elements, most notably calcium and zinc, which are also present in the tarsal claws. A similar elemental distribution is known for adult whip scorpions (Thelyphonida). In P. marginemaculatus, these metal elements are similarly present in adult exuviae. The elemental enrichment of the whip spider exoskeleton is comparable to that present in other members of the Pedipalpi and Tetrapulmonata, reflecting a relatively conserved profile for the few species that have been examined. [ABSTRACT FROM AUTHOR]

In spiders, intersex communication during courtship is essential to avoid the risks of cannibalism due to lack of specific recognition. Parabatinga brevipes (Keyserling, 1891) is a Ctenidae spider with a distribution from Colombia to Uruguay. This study is the first to describe the sexual behavior of P. brevipes, and the fourth reported in the family. We introduced males to females in a cage and recorded their courtship and copulation behavior. Males began courtship after touching female silk, performing Leg-tapping of legs I and Palpal movements. We observed ten copulations that usually occur vertically, in the copulatory position reported for other ctenids, with the male on top of the female, oriented in opposite directions. Copulations usually involve the insertion of one male palp in a single female's genital opening and finish with the pair dropping from the vertical position. These sexual behaviors are compared with reports of other species in the family. [ABSTRACT FROM AUTHOR]

The text is a correction notice from the Journal of Arachnology that highlights a study on spiders feeding on vertebrates. The study reveals that this behavior is more common and widespread than previously believed, with approximately 30% of spider families capable of capturing vertebrate prey. The study distinguishes between habitual vertebrate-eaters and occasional vertebrate-eaters, with ten spider families accounting for 91% of reported vertebrate predation incidents. The findings shed light on spider feeding ecology and the significance of vertebrate prey as a food source for spiders. The text also discusses the feeding habits of spiders that prey on vertebrates, categorizing spider families into two groups: habitual vertebrate-eaters and occasional vertebrate-eaters. It mentions the use of prey-catching webs by spiders and their ability to capture vertebrate prey. The document is a compilation of various scientific articles and publications related to spiders feeding on vertebrates, providing a comprehensive overview of the research conducted on this topic. [Extracted from the article]

The arbanitine spiny trapdoor spiders of the genus Cryptoforis Wilson, Rix & Raven, 2020 are revised, and 15 new species are described from eastern Australia: C. absona sp. nov., C. arenaria sp. nov., C. cairncross sp. nov., C. cassisi sp. nov., C. celata sp. nov., C. cooloola sp. nov, C. fallax sp. nov., C. grayi sp. nov., C. hickmani sp. nov., C. mainae sp. nov., C. montana sp. nov., C. monteithi sp. nov., C. woondum sp. nov., C. xenophila sp. nov., and C. zophera sp. nov. The type species, C. hughesae Wilson, Rix & Raven, 2020, and two other previously described species, C. tasmanica (Hickman, 1928) and C. victoriensis (Main, 1995), are re-described and re-diagnosed, and a key to all species in the genus is provided. Species of Cryptoforis are characterized by 'wafer-door' burrow entrances; the cryptic nature of these burrows in the natural environment likely contributed to the relatively recent recognition of their widespread occurrence in mainland eastern Australia. One species, however, is an exception: C. fallax sp. nov. constructs a 'palisade' type burrow remarkably similar to those created by the turrificus-group in the sister-genus Euoplos Rainbow, 1914. The subtropical region around the McPherson-Macleay overlap appears to be the center of diversity for Cryptoforis; however, given the cryptic nature of burrows, and the confinement of some known species to cool, high elevation habitats (which can be difficult to access and sample), we suggest that additional species likely remain undiscovered in parts of New South Wales and tropical northern Queensland. [ABSTRACT FROM AUTHOR]

Spider webs are characteristic of a species, yet web architecture, the amount of silk laid, and silk mechanics are plastic at an individual level. These different web parameters are influenced by the spiders' own intrinsic state as well as biotic and abiotic conditions. When compared to satiated spiders, hungry spiders are known to build bigger webs, alter the mesh width of the web or increase the frequency of web-building. Although the influence of hunger on web architecture is known in solitary spiders, it has not been studied in social spiders. Here, we examine how prey availability affects the amount of web and cribellate silk laid in the social spider Stegodyphus sarasinorum, Karsch, 1892 (Eresidae). In a laboratory setup, we observed that unfed spiders invest more in web-building, compared to fed spiders. Unfed social spider colonies laid more silk, particularly cribellate silk, than fed colonies. Our results help to shed light on the plasticity of web architecture in social spiders with respect to changes in prey availability. [ABSTRACT FROM AUTHOR]

The Crato Formation (Lower Cretaceous) of Brazil is well known for an exceptionally preserved terrestrial arthropod fossil assemblage. Spiders are relatively abundant, but few have been formally described. A fossil spider belonging to the family Palpimanidae, araneophageous ground-dwelling spiders with distinctly robust front legs, is preserved with the dorsal side hidden within the rock matrix. For the first time, micro-computed tomography (micro-CT) was used to image a fossil spider preserved in a rock matrix, to reveal the dorsal side of this specimen, revealing the eye arrangement, a useful taxonomic character in most spiders, and a deflated abdomen, likely the result of taphonomic processes. The specimen possesses other distinguishing characteristics of Palpimanidae, including an inflated first leg femur, a heavily sclerotized scutum, and a reduced number of spinnerets (2) surrounded by a sclerotized ring. The spider has eight eyes with the lateral pairs extremely close together, a trait suggestive of the subfamily Chediminae. The specimen also possesses an unusual first leg patella with a retrolateral excavation and a thorn-like projection. A new genus is erected, and the spider is named Cretapalpus vittari gen. et sp. nov. A phylogenetic analysis including extant species from each of the subfamilies within Palpimanidae places the fossil at the base of Chediminae þ Otiothopinae. This is the earliest reported fossil palpimanid and first chedimine from South America. A fossil chedimine in South America is not surprising because the South American and African plates were still relatively close during the Early Cretaceous. [ABSTRACT FROM AUTHOR]