Wolf spiders (Araneae: Lycosidae) in the genus Schizocosa Chamberlin, 1904 show a diverse array of male courtship behaviors, signaling modes and morphological traits, and have been the subject of extensive study. Although S. saltatrix (Hentz, 1844) is not as well-studied as some of its congeners, this species occupies a phylogenetic position basal to the well-studied ocreata clade within the genus. Here, we present a detailed analyses of its courtship and provide some insights about multimodal signals in the genus Schizocosa. Male and female S. saltatrix were collected from the field and raised to maturity in the lab, then paired randomly for mating trials, in which courtship and mating behaviors were recorded. Male courtship displays consist of vibratory signals coupled with leg-raising visual signals, suggesting that males apparently use complex (multimodal) signals in courtship despite assumptions from other studies. While the overall amplitude of vibratory signals is not related to mating success, rates and amplitude of some individual components (leg strikes) appear to play a role. Female responses show that variation in visual and vibratory signals is associated with receptivity and mating success, although signal information content (e.g., body condition) is unclear. Although visual displays may serve as attention-altering signals and attract female attention, vibratory signals are more important to receptivity. Recent phylogenies suggest that while leg decorations, extensive leg pigmentation and visual signals have likely been secondarily lost, visual displays are retained in S. saltatrix, perhaps as attention-altering signals.

The reproductive phenology of a species of phalangiid harvestmen, Odiellus aspersus, was studied at Maruyama Park, Sapporo, Hokkaido, for the difference in adult emergence between males and females. At the timepoint in which 50% of the population had matured to adulthood, more females were represented than males, and adult females developed about 10 days earlier on average than males. There was no difference in adult body size between males that had matured earlier and males that were collected later in the season. This fact would conflict with a plausible hypothesis that males should mature slowly to attain larger body size in this species. Elongation of spermatheca in females of the species may explain the marked difference in the adult emergence in the species, by enhancing sperm priority of the males that copulated with females last.

The reproductive phenology of Himalphalangium spinulatum (Roewer, 1911) (Eupnoi: Phalangiidae), which overwinter as juveniles and mature in early summer, was surveyed at a riparian forest on the Sendai River, Tottori City, Honshu, Japan. Females became adults about 3–4 days earlier than males. The body weight of females and males and the number of mature eggs retained in females were highest at the age about a week after the final molting, suggesting a shorter time is needed to commence mating and oviposition in this species. This might be the reason for the shorter time lag in maturation between females and males in this species compared to other species of protogynous harvestmen.

Net-casting spiders (Deinopidae) are cribellate spiders that spin a rectangular, sticky net that is held stretched between the claws of their first two pairs of legs. Deinopids produce eight distinct silk types, but knowledge of the silk-producing morphologies is mostly limited to the spigots associated with different fibers. As there have been no studies of deinopid silk gland structure, we dissected all the silk glands from Deinopis spinosa Marx, 1889 and document their number and morphology. We found silk gland position and morphology consistent with the type and number of silk spigots described for Deinopidae. Notably, for the first time, we describe the silk glands associated with cribellate silk: paracribellate, pseudoflagelliform, and cribellar silk glands. Our findings support the homology of pseudoflagelliform glands with araneoid flagelliform glands and will have importance for informing our understanding of spider web evolution.

Aversive conditioning is a form of associative learning. Here, we investigated learning and memory capacity of the harvester Mischonyx squalidus (Roewer, 1913), to examine the formation of short (STM) and long-term memories (LTM). First, we trained harvesters to associate an aversive stimulus (shock) with a neutral stimulus (tea odor). Each subject went through three consecutive trials, in which pairings between the stimuli lasted for 3s, with intervals of 1 (STM) and 30 (LTM) min. Subsequently, to test memory, we introduced the subjects in a choice arena where they could choose between staying in either of two areas: impregnated with tea chemicals or blank. We did this immediately after the conditioning phase or 24h after it. Both protocols were successful for STM within the same-day test, but not for LTM on the following day. In summary, we provide a new method to train aversive conditioning in harvesters and evidence for short-term memory.

Mexico boasts the highest number of known ricinuleid species worldwide, however the diversity from North America is still poorly known. Herein, we evaluate Pseudocellus pelaezi (Coronado-Gutiérrez, 1970), a dimorphic species distributed in San Luis Potosí and Tamaulipas, northeastern Mexico. This species represents the first known dimorphic species of ricinuleids, well-documented based on morphology, ultrastructure, and genetic distance. The average intraspecific genetic distance (p-distance) at the mitochondrial cytochrome c oxidase subunit 1 (CO1) within P. pelaezi was 4.1%, whereas a much higher value of 14.6% was found between analyzed species of Pseudocellus Platnick, 1980. Although the genetic distance within the species is .4%, the morphology of primary sexual structures such as the male copulatory apparatus of leg III and the female spermathecae were strongly conserved across all the specimens. However, the morphology of a secondary sexual structure, male femora II, showed variation, with some males possessing a thin femora II (morpho 1-M1) (homeomorphic) and others with a wide femora II (morpho 2-M2) (heteromorphic). This male dimorphism, even within the same population of P. pelaezi, might be considered as a direct effect of sexual competition among males to mate with females, however more studies are needed to test this in ricinuleids. This could be done by studying and evaluating the sexual behavior in combination with the genetic evidence from specimens across several populations, offering insight into whether such dimorphism and/or genetic variation is correlated with sexual competition or represents underestimated diversity yet to be described.

Harvestmen are generally considered to be omnivores. In contrast to most other arachnids that are fluid feeders, harvestmen are capable of ingesting solid food particles and may consume invertebrates, small vertebrates, plant tissues, fungi, and detritus. However, for most species, quantitative diet data are lacking. Stable nitrogen isotope analysis provides a means to measure the contribution of these materials to the diet over the time scale of tissue turnover, and thus quantify trophic position. Examination of fecal material can provide additional evidence of recent feeding, which can further complement field observations and isotopic analyses. We investigated the diet of Erginulus clavotibialis (F.O. Pickard-Cambridge, 1905) (Arachnida, Opiliones, Cosmetidae) in western Belize, using stable isotope analysis and scanning electron microscopy of fecal samples. We also examined nitrogen isotopic ratios for carnivores (scorpions and spiders), herbivores (grasshoppers and katydids), and preliminary measures for two other harvestmen species, ants, and termites. Erginulus clavotibialis had δ15N signatures similar to scorpions and spiders, indicating carnivory. Nymphs and adults (females and males) of E. clavotibialis did not differ significantly in their trophic level despite possessing chelicerae and pedipalps that differ substantially in relative size and morphology. Fecal samples contained considerable evidence of arthropod consumption, as fragments of legs and exoskeleton were evident. Our study provides an initial quantification of harvestman diet and documents that E. clavotibialis is primarily carnivorous.

Sticky spiral construction behavior in orb-weaving spiders is strikingly flexible: 10 to 16 different cues influence the hundreds of decisions that a spider makes while building the sticky spiral in an orb. Several variables that are influenced by radial tensions, including the frequencies and amplitudes of vibrations and the extensibility and tensions of the radii, have been repeatedly mentioned as possible cues guiding sticky spiral placement. Nevertheless, previous studies have suggested that radius tensions do not affect sticky spiral spacing. These tests were complicated, however, by the tight correlations between variables due to the highly regular geometry of orbs, possible context-dependent variation in the use of cues, and the intrinsic difficulty of demonstrating the absence of an effect. Greater certainty regarding tension-dependent cues is crucial for understanding the cues guiding orb construction, so this study extends these experiments, examining the effects of both increasing and decreasing radius tension, and of different sequences and magnitudes of changes. The results confirm previous findings: changes in radius tensions did not influence sticky spiral spacing decisions in consistent ways and generally failed to produce statistically significant effects. I argue that the likely reason why spiders do not use tension-dependent variables to guide sticky spiral placement is that such cues are unreliable because the spider's own weight substantially alters the tensions on nearby web lines in complex and variable ways.

During a study of the pseudoscorpion fauna of caves in northeastern Brazil, a new species of the genus Neoallochernes Hoff, 1947 was discovered. Morphological analysis suggests that the new species, named Neoallochernes catimbauensis sp. nov., is closely related to N. cubanus Muchmore, 1992. Neoallochernes catimbauensis can be distinguished from other congeners by its spermathecae morphology, trichobothria ib and ist positioned subbasally, trichobothrium isb located subdistally to the middle of the finger and proximal to est. Femur length/width ratios were 2.83× (♀) and 2.42–2.62× (♂); patella width ratios were 2.34× (♀) and 2.29–2.31× (♂); and chela (without pedicel) ratios were 3.34× (♀) and 3.18–3.21× (♂). In addition, ecological observations, distribution maps including past and present records, and a taxonomic identification key are provided.

Scorpions are diverse and abundant in tropical and subtropical regions worldwide, especially in arid ecosystems where they play a relevant role as predators. However, few studies have examined diet composition, use of alternative foraging strategies, prey selection, and predator-prey size relationships of scorpions in different microhabitats. This study provides an analysis of the diet of Buthus montanus Lourenço & Vachon, 2004 in an arid area of SE Spain. Prey captured by scorpions were recorded during black-light censuses over the main activity season of B. montanus in the study area. Because scorpions were observed capturing prey on the ground surface, below ground, and in vegetation, prey availability was estimated using complementary methods for shrub- and ground-dwelling prey. Results show that B. montanus is a generalist predator that feeds on a diverse array of prey, although predatory arthropods and tenebrionid larvae comprised the highest proportion of its diet in both number of prey and biomass. Cannibalism was a major component of its diet, accounting for almost 25% of the biomass ingested, especially in large scorpions. The composition of the diet, prey-size variability, and predator-prey size relationship showed size-related differences. These size-related variations in the diet were also linked to habitat use, due to climbing vegetation by smaller scorpions. These results highlight the implications of ontogenetic shifts in the diet of B. montanus related to cannibalism by larger scorpions and climbing vegetation by smaller individuals, causing changes in the type of prey used by individuals of different size and predator-prey size relationships.

Australia is home to an incredible diversity of spiders, but much of their biology remains unstudied. The orb-weaving spiders (family Araneidae) are especially diverse and frequently encountered, yet the ecology of very few species has been explored. The common name “Australian garden orb-weaver” refers to several species, including Hortophora transmarina (Keyserling, 1865), found mostly along Australia's east coast, and Hortophora biapicata (L Koch, 1871), found mostly along Australia's south and south-eastern coasts. These two similar species are large, nocturnal orb-weavers that occupy a wide range of both natural and anthropogenically disturbed habitats. Here, I describe the general morphology, habitat use, diet and foraging behavior, key predators, laboratory rearing, and mating dynamics of these common but understudied spiders. This information was gathered via field observations, laboratory experiments, and literature reviews. These spiders provide a useful system for studying a number of aspects of spider biology, including mating systems, predation, anti-predator defences, and nocturnal behaviors.

Although courtship and mating behaviors have been described for nearly all scorpion lineages, intrasexual interactions in scorpions remain understudied. Recently, a novel ritualized behavioral unit, termed “arm-span competition,” in which individuals face off and extend their pedipalps laterally, was described from analyses of male-male contests in several scorpionid species. Here, we present the first documented observation of arm-span competition in a buthid scorpion, Tityus cf. rosenbergi Pocock, 1898. Interestingly, both T. cf. rosenbergi and most scorpionid species known to engage in arm-span competition exhibit a similar sexual dimorphism: males have markedly longer and more slender pedipalps than females. We suggest that the elongated pedipalps in males of these species might be the result of selective pressure related to ritualized arm-span competition. We also highlight the potential for citizen science to contribute rare observations to scientific literature.

Vinegaroons in the high desert grasslands of southeastern Arizona spend much of the year in deep sealed underground cells and dig to the surface when the first summer rains begin in late June or during July. They are active only at night, when they are large apex ambush predators that prey on a variety of small, surface-dwelling animals. Adult and last instar immature vinegaroons were frequently observed, whereas the smaller first three instars were rarely seen. Using mark-capture techniques, the density of individuals in the area was found to be at least 95 individuals/ha to as high as 680 individual/ha. The population profile remained mostly steady over several years with adults and 4^th instar immatures constituting 90% of the observed population. Females were mainly present during the earlier part of the foraging season. In contrast, males were active much longer and until the end of season. The three first instars of vinegaroons spent little time on the surface of the ground partly because they are vulnerable to predators and partly because they require few prey items to accumulate the necessary reserves for molting to the next instar. About 12% of the population had injuries, or signs of previous injuries. Most injuries were to their tail-like flagellum, with a few sensory leg injuries. Short, regrown flagella in field individuals showed their ability to regenerate these lost appendages and laboratory experiments demonstrated that vinegaroons can regenerate lost parts of sensory legs and even their hard, powerful pedipalps.

Orb webs constructed by members of the spider family Uloboridae are characterized by the presence of cribellate thread on frame lines and cribellate thread placed on radii to form zig-zag patterns in a web's perimeter. Both features are added before more typical, fully circular capture spiral production begins. Zig-zags give the impression that a spider is filling in the gaps between a web's outermost spiral and frame line, although they are constructed before capture spiral turns begin. We examine these traits in orb webs of six species (Philoponella vicina (O. Pickard-Cambridge, 1899), Siratoba referens (Muma & Gertsch, 1964), Uloborus glomosus (Walckenaer, 1841), Uloborus trilineatus Keyserling, 1883, Waitkera waitakerensis (Chamberlin, 1946), and Zosis geniculata (Olivier, 1789). In four species, the distance between the outermost capture spiral and frame line was correlated with the length of cribellate thread on a radius. A web's capture area increased as the area encompassed by zig-zags was added to that encompassed by the outermost fully circular cribellate spiral thread and again when cribellate thread on frame lines was included. When constructed in frames of the same size, webs of S. referens and U. glomosus were less symmetrical and contained more capture thread switchbacks per spiral turn and per web area than did horizontal orb webs of Leucauge venusta (Walckenaer, 1841) (family Tetragnathidae). Features in the perimeter of uloborid webs may adapt these small spiders to irregular spaces within vegetation by allowing them to cover larger portions of their webs with sticky lines.

A morphological study of the type material of two Colombian theraphosid species in the genus Thalerommata Ausserer, 1875, deposited in the European spider collections of the Natural History Museum, London, and Muséum national d'Histoire Naturelle, Paris, enables us to establish a new synonym: T. macella (Simon, 1903) is designated as a junior synonym of T. gracilis Ausserer, 1875.

The Paratropididae Simon, 1889 comprises small to medium-sized (6.0–18.5 mm) mygalomorph spiders with 26 species distributed in four genera: Anisaspis Simon, 1892; Anisaspoides F. O. Pickard-Cambridge, 1896; Paratropis Simon, 1889 and Stormtropis Perafán, Galvis & Pérez-Miles, 2019. Paratropidids can be found in tropical and mountain forests, in caves, near rivers, under fallen logs and rocks, leaf litter, moss and ravines. Most species are distributed in South America, mainly in Colombia, Ecuador and Brazil. Despite recent efforts in understanding the taxonomy of the family, paratropidids are still poorly studied. Herein, three new species of Paratropis are described: Paratropis celiae sp. nov. and Paratropis manauara sp. nov., both from Manaus in the state of Amazonas, Brazil; and Paratropis vulcanix sp. nov. from Departamento Tolima-Calda Nevado del Ruiz, Colombia. An updated geographical distribution map for the entire genus is presented and a discussion on the taxonomic problems of the family is provided.

Spiders use information received from trichobothria for capturing prey or escaping predators. However, we have no extensive information on if or how trichobothria might be used in conspecific communication. This study tests the hypothesis that female wolf spiders Schizocosa retrorsa, (Banks, 1911) use their foreleg trichobothria to detect and assess courting males. Prior studies have shown that male S. retrorsa can mate successfully in signaling environments where females cannot detect visual or vibratory signals. Despite this, higher rates of male leg waving still predicted successful mating. In addition to their visual conspicuousness, these rapid leg waves can generate air particle movement that may be detectable by a female's trichobothria. If females use trichobothria to detect and assess male leg waving, then we might predict the following. When female trichobothria are compromised, we expect (i) lower overall mating success and (ii) no relationship between male mating success and leg waving rate. To test these predictions, we ran mating trials in environments unconducive to visual or vibratory signals and compared the mating success and mating predictors of female/ male S. retrorsa pairs across two female treatments groups: (a) foreleg trichobothria unablated and (b) ablated. We found no significant difference between the mating success of the two groups. However, mating success was higher for males that waved their legs at a faster rate in the unablated, but not the ablated treatment groups. Our results indicate that the ablation of female trichobothria interferes with the detection and assessment of male leg waving, supporting a role of trichobothria in receiving air particle movement signals.

The range of trophic niches in spiders varies from very wide, including prey of several insect orders, other arthropods, and even nectar and other plant products, to very narrow, restricted to specific prey types, such as ants. Previous studies showed that the effects of a mixed diet are beneficial to fecundity, survivorship, and growth rate for some species but not others. This study evaluated the impact of a varied diet and monotypic diets of beetles, ants, and termites for Tidarren haemorrhoidale (Bertkau, 1880) a cobweb spider. Adult females were collected in a Eucalyptus plantation, kept in captivity, and divided into four experimental groups; each submitted to one of these diets for 125 days. Beetles were valuable prey for proteins and lipids compared to the alternatives. Termites and ants had equivalent contents of proteins, but termites were richer in lipids. Two monotypic diets composed of the main prey types (beetles and ants) had similar effects on fecundity and body mass compared to the mixed diet. Although termites have more lipids than ants and have a higher proportion of their biomass consumed, the monotypic diet of termites caused weight loss for spiders over time and reduced fecundity. Survivorship in all groups was similar. These results indicate that a diversified diet is not required for T. haemorrhoidale to achieve its maximum reproductive potential. This characteristic may be important to ensure the success of this species in colonizing and establishing large populations, even in disturbed habitats with low prey diversity.

Biomaterials are becoming increasingly popular in solving applied problems. Aciniform silk (wrapping silk) is one of the seven known types of silk secretions orb-web spiders produce. It has an impressive set of mechanical properties suggesting a high, hereto unexplored potential for textile and biomedical applications. Here we have summarized existing knowledge and identified the gaps in our understanding of the structure, functions, properties and biology of aciniform silk. Aciniform silk is composed of the protein aciniform spidroin (AcSp), which is characterized by relatively lower percentages of alanine and glycine than dragline silk. The specific mix of alpha helices and beta sheets is believed to bring about its great toughness and elasticity. The combination of high toughness and extensibility makes swathes of aciniform silk an ideal tool to keep the prey wrapped, but also for the protective encasing of spider egg clutches. Understanding of the relationship between the composition, properties and biological functions of aciniform silk is still rudimentary, as current studies are mostly mono-focal and barely apply an integrative approach. Closing this gap requires better integration of material science with ecological and evolutionary aspects. This will not only benefit a better understanding of why and how animals use silks, but it will also enable the production of better silk-inspired biomaterials with superior properties.

We examined the role of lycosid eye rows and the pairs of eyes within each row in prey detection and mate recognition by Schizocosa ocreata (Hentz, 1844) using two approaches: (1) occluding anterior or posterior eye rows; and (2) occluding all but a single eye pair. In response to live prey, females took longer to orient and approach crickets when the posterior eye row was occluded; responses were intermediate when the anterior eye row was occluded. With six of eight eyes occluded, spiders that could see with posterior lateral eyes (PLE-only) detected the cricket as quickly as the fully sighted spiders (controls), while spiders limited to seeing from other eye pairs took longer to orient towards prey. Orientation distance varied significantly as well, with Control, ALE-only, PME-only and PLE-only spiders responding at greater distances than AME-only spiders. To analyze the functions of the eye rows involved in mate preference in S. ocreata, we conducted an additional study with presentation of video playback of a courting male to females with different eye rows occluded. Females with their posterior eyes occluded took longer to orient and respond compared to controls and anterior eye row occlusion. The sum of female receptivity displays was also significantly reduced when posterior eyes were occluded, suggesting the posterior eyes may be involved in mate recognition. Taken together, these data suggest that the posterior (secondary) eyes may have an important role in detection and identification of both prey and courting males.

Antibiotic resistance is a global health crisis. Our current arsenal of antibiotics—drugs meant to kill bacteria and stop their population growth—is becoming less effective at treating bacterial infections as resistant bacteria emerge, fueling the dire need to discover new antibiotics. Most antibiotics in use today have been discovered from bacteria. To increase the chances of finding potentially novel antibiotic molecules, we studied the relatively unexplored microbial environment of scorpion tissues, using the giant sand scorpion, Smeringurus mesaensis (Stahnke, 1957). Bacterial symbionts were isolated and cultured from the mesosoma and metasoma, and isolates were tested in a functional assay for production of antibiotics. Under the culture conditions utilized, most scorpion-derived bacteria were from the phyla of Firmicutes, Proteobacteria and Actinobacteria. Fifty-five percent of the clonal isolates tested produced antibiotics, with most being Bacillus species. None of the bacterial conditioned media were cytotoxic to mammalian cells. This study suggests scorpion tissues may provide a rich source of antimicrobial molecules to help combat the antibiotic resistance crisis.

Harvester species exhibit a diverse array of defenses against predators. In this article, we briefly cover chemical defenses, coloration patterns, autotomy, aggregations, freezing behavior, bobbing, body vibration, and the production of sounds that might be used to avoid predators' attacks. Those defenses are not present in all harvester species and may not deter all kinds of predators. We discuss how prey-predator interaction may shape the evolution of defenses. Here we focus on studies that have been done after 2007, and we aim to give a general idea of the knowledge about prey-predator interactions in Opiliones to date, especially to the general public.

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.

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.

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.