Pselaphochernes distinctus is a species of pseudoscorpion in the family Chernetidae. Pseudoscorpions are small, flattened arachnids that resemble true scorpions but lack a tail and stinger. Members of the genus Pselaphochernes are typically found in association with soil, leaf litter, or decaying organic matter in forested habitats. This species is part of a diverse group of pseudoscorpions that play roles as micro-predators in soil ecosystems.
hooded tickspider
Pseudocellus dorotheae is a species of hooded tickspider in the order Ricinulei, first described from Texas in 1939. Ricinuleids are a small, reclusive order of arachnids characterized by a retractable hood (cucullus) covering the mouthparts. This species represents one of the few described members of the genus Pseudocellus in North America. Like other ricinuleids, it is poorly known due to its cryptic habits and limited collection records.
Pseudogarypus banksi is a species of pseudoscorpion in the family Pseudogarypidae, described by Jacot in 1938. It belongs to a small family of false scorpions characterized by their distinctive morphology among pseudoscorpion lineages. The species is documented from North America, though detailed biological information remains limited in available literature.
pseudoscorpions, false scorpions, book scorpions
Pseudoscorpions are tiny arachnids, most under 5 mm in length, superficially resembling scorpions but lacking a stinger and elongated tail. They are among the oldest terrestrial colonizers, with fossils dating to the Middle Devonian (ca. 390 million years ago). Despite their ancient lineage, they exhibit remarkable morphological stasis, with even Devonian fossils appearing modern. Most species inhabit concealed microhabitats such as beneath bark, in leaf litter, soil, caves, or mammal nests, making them seldom encountered despite being fairly common. They are predatory, seizing small invertebrate prey with venomous pincer-like pedipalps.
Pseudouroctonus is a genus of vaejovid scorpions established by H. L. Stahnke in 1974. The genus contains approximately 20 species distributed across the drylands and mountains of western North America. Members of this genus are notable for their stenotopic habitat requirements and have been subject to recent taxonomic revision using molecular methods, which has revealed substantial cryptic diversity. The genus includes the P. minimus complex, a group whose diversification patterns have been used to study the relative impacts of pre-Quaternary tectonics versus Pleistocene climate change on speciation.
Texas Cave Scorpion
Pseudouroctonus reddelli, commonly known as the Texas Cave Scorpion, is a troglobitic scorpion species first described in 1972. It belongs to the family Vaejovidae and is endemic to cave systems in Texas. The species exhibits classic cave-adapted traits including reduced pigmentation and elongated appendages. As a specialized cave dweller, it represents an important component of subterranean biodiversity in the karst regions of central Texas.
Pseudouroctonus santarita is a species of scorpion in the family Vaejovidae, described by Ayrey and Soleglad in 2015. The species belongs to a genus of scorpions found in western North America. Like other members of Pseudouroctonus, it is a small to medium-sized scorpion adapted to specific habitats in arid and semi-arid regions. The genus has been subject to recent taxonomic revision using molecular data to clarify species boundaries.
cellar spider
Psilochorus imitatus is a cellar spider species in the family Pholcidae, first described by Gertsch and Mulaik in 1940. It is known from the United States and Mexico. As a member of Pholcidae, it likely exhibits the characteristic long, slender legs and small body typical of this family, though specific morphological details for this species remain limited in published sources.
Pterygosomatoidea is a superfamily of mites within the order Trombidiformes. These arachnids are part of the diverse Prostigmata lineage, which includes many parasitic and predatory mite groups. The superfamily encompasses several families of mites that are primarily associated with reptiles as hosts. They represent a specialized evolutionary radiation within the Eleutherengona infraorder.
Salticus palpalis is a species of jumping spider in the family Salticidae, first described by Banks in 1904. It belongs to a genus known for its excellent vision and active hunting behavior. The species has been recorded in the United States and Mexico.
Scopoides cambridgei is a species of ground spider in the family Gnaphosidae. The species was described by Gertsch and Davis in 1940. It is known from the United States and Mexico. No specific ecological or behavioral studies have been documented for this species.
dwarf spider
Scylaceus pallidus is a dwarf spider species in the family Linyphiidae, first described by Emerton in 1882 under the basionym Tmeticus pallidus. The species is distributed across the United States and Canada. As a member of the sheet-web weaving family Linyphiidae, it constructs flat horizontal webs for prey capture. The genus Scylaceus comprises small-bodied spiders, with this species representing one of the Nearctic representatives of this primarily Palearctic genus.
Segestria is a genus of spiders in the family Segestriidae. These spiders are characterized by their elongated, cylindrical bodies and six eyes arranged in a distinctive semicircular pattern. The genus has a primarily Eurasian distribution, with some species extending to the Americas, North Africa, Madagascar, and New Zealand. Segestria species are known for building tubular retreats in cracks and crevices, from which they hunt prey using silk triplines.
Flatties, Crescent-eyed Spiders, Wall Crab Spiders
Selenops is a genus of spiders in the family Selenopidae, commonly known as "flatties" due to their extremely flattened bodies. The genus comprises approximately 132 species distributed across arid and semi-arid regions worldwide, including the southwestern United States, Florida, the Caribbean, and tropical regions of Asia, Africa, and the Americas. These spiders are notable for being the first documented arachnids capable of controlled gliding when falling, using their flattened bodies and laterigrade legs to steer toward tree trunks rather than falling to the ground. They exhibit some of the fastest turning movements recorded in terrestrial legged animals when attacking prey from behind.
flatty
Selenops submaculosus is a species of wall crab spider in the family Selenopidae, commonly known as a "flatty." It exhibits the characteristic extremely flattened body and laterigrade leg posture typical of the family. The species occurs in the southeastern United States, the Bahamas, Cuba, and the Cayman Islands. Like other selenopids, it is nocturnal and typically found on vertical surfaces.
Septentrinna bicalcarata is a species of true spider in the family Corinnidae, first described by Eugène Simon in 1896. The species is recorded from the United States and Mexico. It belongs to a small genus of ground-dwelling spiders within the ant-mimic spider family Corinnidae. Published information on its biology and ecology remains limited.
Sergiolus decoratus is a species of ground spider in the family Gnaphosidae, first described by Kaston in 1945. Like other members of the genus Sergiolus, it is known for its bold, colorful markings that may serve as mimicry of velvet ants (Mutillidae). The species is found in North America, with records from the United States and Canada including Alberta and Manitoba.
Serradigitus wupatkiensis is a scorpion species in the family Vaejovidae, first described by Stahnke in 1940. It belongs to the genus Serradigitus, which is characterized by serrated or toothed structures on the pedipalp fingers. The species is found in North America, with the specific epithet referencing Wupatki, likely indicating a type locality in the southwestern United States. Like other vaejovid scorpions, it is a small to medium-sized species adapted to arid environments.
Singa keyserlingi is a species of orb-weaving spider in the family Araneidae, first described by McCook in 1894. It is known from the United States and Canada. As an orb weaver, it constructs spiral wheel-shaped webs for prey capture. Information regarding its specific biology, habitat preferences, and detailed morphology remains limited in published sources.
mite harvestman
Siro boyerae is a species of mite harvestman in the family Sironidae. It was originally described as Neosiro boyerae by Giribet & Shear in 2010, and was previously placed in the genus Siro before taxonomic revision. This small arachnid belongs to the suborder Cyphophthalmi, a group of primitive harvestmen characterized by their eyeless condition and compact body form.
Siro kamiakensis is a species of mite harvestman, a small arachnid in the family Sironidae. It was described by Newell in 1943 and is currently classified under the genus Neosiro, though it was historically placed in Siro. The species is found in North America, with records from the Pacific Northwest region of the United States.
Siro sonoma is a species of mite harvestman in the family Sironidae. It was originally described by Shear in 1980 and placed in the genus Siro. In 2022, the genus Arhesiro was erected to accommodate this species and Siro clousi, with S. sonoma becoming Arhesiro sonoma. As of 2023, taxonomic sources vary in their treatment, with some recognizing Arhesiro sonoma as the accepted name while others retain Siro sonoma. The species is known only from Sonoma County, California.
Sisicottus quoylei is a species of dwarf spider described by Miller in 1999. It belongs to the family Linyphiidae, one of the largest families of spiders, commonly known as sheet-web weavers or money spiders. The species has been documented in North America.
dwarf spider
Sisicus penifusifer is a species of dwarf spider in the family Linyphiidae, described by Bishop and Crosby in 1938. It belongs to a genus of small sheet-web weavers. The species has been documented in parts of the United States and Canada, with records from Alberta, British Columbia, and Manitoba.
armoured harvestman
Sitalcina sura is a species of armoured harvestman in the family Phalangodidae, described by Briggs in 1968. It belongs to the suborder Laniatores, a diverse group of harvestmen characterized by relatively short legs and often heavily armoured bodies. The species is known to occur in North America. As with many phalangodid harvestmen, detailed ecological and behavioral information remains limited in published literature.
Smeringurus vachoni immanis is a subspecies of scorpion in the family Vaejovidae, native to the southwestern United States. It belongs to a genus characterized by distinctive metasomal (tail) morphology. The subspecies designation indicates geographic or morphological differentiation from the nominate form S. vachoni vachoni. Like other members of Smeringurus, it is adapted to arid environments and exhibits fossorial or nocturnal habits typical of desert scorpions.
Smeringurus vachoni vachoni is a subspecies of scorpion in the family Vaejovidae. It belongs to a genus of small to medium-sized scorpions found in arid regions of western North America. The nominate subspecies is distinguished from the other subspecies, S. v. mesaensis, primarily by geographic distribution.
Funnel-web Wolf Spider
Sosippus janus is a species of wolf spider in the family Lycosidae, first described by Brady in 1972. It is one of six Sosippus species known from the United States. Unlike most wolf spiders, members of this genus are web-builders, constructing sheet-like webs with funnel-like retreats. The species is found in the southern United States.
funnel-web wolf spider
Sosippus mimus is a web-building wolf spider in the family Lycosidae. Unlike most wolf spiders, which are nomadic hunters, species in the genus Sosippus construct sheet-like webs with funnel-shaped retreats. This species is found in the United States and shares the distinctive eye arrangement typical of lycosids: two large posterior median eyes with four smaller eyes below and two lateral eyes flanking them.
Dwarf Cellar Spiders
Spermophora is a genus of cellar spiders established by Nicholas Marcellus Hentz in 1841. It belongs to the subfamily Pholcinae within the family Pholcidae. The genus contains 45 recognized species distributed across Africa, Europe, Oceania, Asia, the United States, and Brazil. Members are commonly referred to as Dwarf Cellar Spiders.
Steatoda grandis is a species of cobweb spider in the family Theridiidae, first described by Banks in 1901. It is known from the United States, though specific details about its biology and ecology remain poorly documented in the scientific literature. The species belongs to a genus that includes several well-known spiders, some of which are frequently encountered in human dwellings.
Steatoda mexicana is a cobweb weaver spider (family Theridiidae) described by Herbert W. Levi in 1957. It is native to Mexico and the southwestern United States. Like other Steatoda species, it constructs irregular tangled webs and is a member of the same genus as the well-known Triangulate Cobweb Weaver (S. triangulosa) and the Noble False Widow (S. nobilis). Very little specific information has been published about the biology of this particular species.
Steatoda washona is a cobweb spider in the family Theridiidae, described by Gertsch in 1960. It belongs to a genus that includes several species commonly known as false widows due to their resemblance to black widows (Latrodectus). The species occurs in the southwestern United States and Mexico. Like other Steatoda species, it constructs irregular tangled webs and is typically found in sheltered microhabitats.
short-tailed whipscorpions
Stenochrus is a genus of hubbardiid short-tailed whipscorpions (order Schizomida) first described by Ralph Vary Chamberlin in 1922. The genus was historically considered a 'junkyard' taxon containing morphologically disparate species, but integrative systematics using molecular and morphological data has redefined its boundaries. As currently circumscribed, Stenochrus comprises approximately ten species distributed primarily in Mexico, Central America, and the Caribbean. The most widespread species, Stenochrus portoricensis, exhibits exceptional geographic range due to parthenogenetic reproduction and ecological tolerance, with introduced populations established in South America and Europe.
Strotarchus beepbeep is a spider species in the family Cheiracanthiidae, described in 2012. The species is characterized by orange coloration on the carapace, legs, and abdomen, with pale margins on the carapace and reddish-brown chelicerae. Its specific epithet references the sound of the Road Runner cartoon character.
Syarinus is a genus of pseudoscorpions in the family Syarinidae, established by J. C. Chamberlin in 1925. The genus contains approximately six described species distributed across North America and Europe. Members of this genus are small arachnids belonging to the suborder Iocheirata, characterized by their venomous pedipalps used to capture prey.
Synageles bishopi is a species of ant-mimicking jumping spider in the family Salticidae. It is native to the continental United States. Like other members of its genus, it exhibits Batesian mimicry of ants, holding its second pair of legs aloft to simulate antennae. The species was described by Cutler in 1988.
Synageles occidentalis is a species of jumping spider in the family Salticidae, first described by Cutler in 1988. The species is known from the United States and Canada, with distribution records from Alberta and British Columbia in Canada. As a jumping spider, it likely exhibits the characteristic visual hunting behavior and salticid morphology typical of the family, though specific behavioral and ecological details for this species remain poorly documented.
Tapinocyba cameroni is a species of sheet-web weaving spider in the family Linyphiidae, described in 2007 from Canada. The species is known from the prairie provinces of Alberta, Manitoba, and Saskatchewan. As a member of the dwarf spider family Linyphiidae, it is likely small-bodied with typical linyphiid morphology including reduced eyes and specialized setae on the tarsi.
Simple Sheet-web Weaver
Tapinocyba simplex is a species of dwarf spider in the family Linyphiidae, commonly known as sheet-web weavers due to their characteristic web architecture. The species was described by James Henry Emerton in 1882. It is one of approximately 4,700 species in Linyphiidae, the second-largest spider family. Records indicate presence in the United States and Canada (Alberta, British Columbia, Manitoba).
Taracus packardi is a species of harvestman (Opiliones) in the family Taracidae. First described by Simon in 1879, this species occurs in North America. The taxon was revised in 2016, with Taracus nigripes Goodnight & Goodnight, 1943 synonymized with T. packardi.
Taracus silvestrii is a species of harvestman in the family Taracidae, described by Roewer in 1929. It belongs to the suborder Dyspnoi, a group of long-legged arachnids commonly known as harvestmen or daddy longlegs. Members of the genus Taracus are characterized by their elongated body form and exceptionally long, slender legs relative to body size. The species is known from limited collection records in North America.
prowling spider
Teminius affinis is a species of prowling spider in the family Miturgidae, first described by Banks in 1897. It occurs in the southern United States and Mexico. As a member of the prowling spider family, it is likely an active hunter rather than a web-builder, though specific behavioral observations for this species are limited in the available literature.
Teminius insularis is a spider species in the family Miturgidae, first described by Lucas in 1857. It is widely distributed across the Americas, ranging from the southern United States through the Greater Antilles to Argentina, with records from multiple Brazilian states and French Guiana. The species has accumulated over 1,100 observations on iNaturalist, indicating it is moderately well-documented. As a member of Miturgidae, it belongs to a family of wandering spiders that do not build permanent webs for prey capture.
long-jawed orb weaver
Tetragnatha straminea is a species of long-jawed orb weaver spider in the family Tetragnathidae. It is found across northern North America, including the United States, Canada, and Cuba. Like other members of the genus Tetragnatha, it possesses elongated chelicerae and a slender body adapted for camouflage. The species was described by Emerton in 1884.
whipscorpions, vinegaroons, whip-scorpions
Thelyphonidae is the sole family of the arachnid order Uropygi (Thelyphonida), containing approximately 140 described species in 25 genera (16 extant, 9 fossil). Members are commonly known as whipscorpions or vinegaroons due to their whip-like flagellum and defensive secretion of acetic acid. The family is divided into four subfamilies: Hypoctoninae, Mastigoproctinae, Thelyphoninae, and Typopeltinae. Despite their conspicuous appearance and wide tropical distribution, systematic knowledge of the group has advanced slowly.
Theridion californicum is a species of cobweb spider in the family Theridiidae. It has been documented in the United States and Canada. As a member of the Theridiidae, it constructs irregular, three-dimensional webs for prey capture.
Different Cobweb Spider
Theridion differens is a species of cobweb spider in the family Theridiidae. It is found in the United States and Canada, with records from Alberta and British Columbia. The species was described by Emerton in 1882. As a member of the genus Theridion, it constructs the irregular, three-dimensional webs characteristic of this group.
Theridion petraeum is a cobweb spider in the family Theridiidae, described by L. Koch in 1872. The species has a broad distribution spanning North America, Europe, North Africa, the Caucasus, and Russia extending to the Far East and Kazakhstan. Records indicate presence across multiple continents including Africa and northern Asia. As a member of Theridiidae, it constructs irregular three-dimensional webs, though specific details of its biology and ecology remain poorly documented in available sources.
Theridion submissum is a species of cobweb spider in the family Theridiidae. The species was described by Gertsch and Davis in 1936. It is found in the United States, Mexico, the Bahama Islands, and Jamaica. Like other members of the genus Theridion, it constructs irregular three-dimensional webs.