Stearns' sea spider
Pycnogonum stearnsi is a sea spider in the family Pycnogonidae, found on the Pacific coast of North America and in Japan. It reaches about 2.5 cm in length and lacks eyes, chelicerae, and pedipalps—unusual traits among sea spiders. It feeds by inserting its barrel-shaped proboscis into soft-bodied prey and sucking fluids. Males carry egg masses on specialized ovigerous legs.
banded rove beetle
Quedius cinctus is a large rove beetle in the family Staphylinidae. It is native to Europe and parts of Asia and North Africa, with introduced populations in eastern North America. The species is characterized by its relatively large size among rove beetles and the distinctive banded pattern on its elytra. Like other members of its genus, it is a ground-dwelling predator found in forested and riparian habitats.
Spelean Rove Beetle
A troglophilic rove beetle found in porcupine dung caves in Nova Scotia, where it functions as the dominant invertebrate predator. The pupal stage was described for the first time from Nova Scotian populations. Late-instar larvae excavate and occupy cavities within dung deposits, pupating in these constructed chambers. The species shows an apparently disjunct distribution pattern in Nova Scotia, possibly reflecting post-glacial colonization from Atlantic refugia.
water stick-insect, water scorpion, water mantis
Ranatra is a genus of slender aquatic predatory insects in the family Nepidae, commonly called water stick-insects or water scorpions. The genus contains over 140 species distributed across freshwater habitats worldwide, with highest diversity in South America and Asia. These insects are sit-and-wait predators that use raptorial forelegs to capture prey. They possess a distinctive long caudal siphon for breathing while submerged.
Western Waterscorpion
Ranatra brevicollis is a species of waterscorpion in the family Nepidae, first described by Montandon in 1910. It is distributed across Central America and North America. The species belongs to a genus of aquatic predatory insects commonly known as waterscorpions due to their elongated, scorpion-like appearance. It is recognized by the common name Western Waterscorpion.
Ranatra drakei is a species of water scorpion in the family Nepidae, described by Hungerford in 1922. Like other members of the genus Ranatra, it is an aquatic predatory insect with raptorial forelegs adapted for capturing prey. The species is known from North America, though specific ecological details remain poorly documented in published literature.
brown water scorpion, brown waterscorpion
Ranatra fusca is a predatory aquatic bug in the family Nepidae, commonly called the brown water scorpion. Native to North America, it inhabits freshwater environments where it hunts small invertebrates using raptorial forelegs. Adults reach 3.2–4.2 cm in length and possess a long respiratory siphon for breathing at the water surface. The species is most active from spring through autumn.
Montezuma waterscorpion
Ranatra montezuma is a waterscorpion species endemic to Montezuma Well, a thermally constant, fishless spring in Yavapai County, Arizona. It was described by J. Polhemus in 1976 and represents a highly localized population with specific dietary adaptations to its unique aquatic environment. The species exhibits nocturnal foraging behavior and maintains high population densities supported by abundant endemic prey.
waterscorpion
Ranatra quadridentata is a species of waterscorpion described by Stål in 1862. As a member of the family Nepidae, it is an aquatic predatory insect that inhabits freshwater environments. The species has been documented in Central America and North America, with 188 observations recorded on iNaturalist.
Raphidiid Snakeflies, Snakeflies
Raphidiidae is the largest family of snakeflies in the order Raphidioptera, comprising over 200 extant species. Members are characterized by an elongated prothorax that gives them a distinctive 'snake-like' appearance. The family is distributed across the Northern Hemisphere, with notable diversity in North America, Europe, and Asia. The genus Alena is considered the most morphologically distinct within the family due to unusual male genital sclerites. Snakeflies in this family are predators of small arthropods.
snakeflies
Raphidioptera, commonly known as snakeflies, is an order of predatory holometabolous insects comprising approximately 260 species in two families: Raphidiidae and Inocellidae. The order is distinguished by an elongated prothorax that creates a 'neck-like' appearance, giving rise to their common name. Snakeflies are considered living fossils, with modern species closely resembling forms from the early Jurassic period 140 million years ago. They are primarily arboreal predators of small insects, most commonly associated with wooded habitats and tree bark.
Assassin Bugs, Ambush Bugs, Kissing Bugs, Wheel Bugs, Thread-legged Bugs, Bee Assassins, Millipede Assassins, Masked Hunters
Reduviidae is a large cosmopolitan family of true bugs (Hemiptera: Heteroptera) comprising approximately 7,000 described species across more than 20 subfamilies. The family is predominantly terrestrial and predatory, with members employing diverse hunting strategies including ambush predation, active pursuit, and specialized prey capture using modified forelegs or sticky secretions. A notable exception is the subfamily Triatominae, whose members are hematophagous ectoparasites of vertebrates and vectors of Chagas disease. Most species possess a distinctive narrow neck, sturdy body, and curved proboscis that fits into a stridulatory groove on the prosternum, producing sound when rubbed against ridges. The family exhibits remarkable morphological diversity, with body sizes ranging from 12 to 36 mm and coloration spanning cryptic browns and blacks to aposematic reds, oranges, and metallic blues.
Reduvius is a large genus of assassin bugs (family Reduviidae) containing approximately 197 species. The genus is one of the most speciose in the assassin bug family. Most species occur in arid and semi-arid regions of the Afrotropical, Oriental, and Palearctic realms. Only three species are New World endemics, with Reduvius personatus (the masked hunter) being cosmopolitan and introduced to the Western Nearctic. Species range from 8–22 mm in length.
Masked Hunter
Reduvius personatus, commonly known as the masked hunter, is a cosmopolitan assassin bug recognized for the distinctive debris-camouflaged appearance of its nymphs. The species is a generalist predator of small arthropods and has been introduced to multiple continents through human activity. Adults are uniformly dark brown to black, winged insects measuring 17–22 mm, while nymphs appear gray or light-colored due to accumulated dust and lint on their bodies. Though beneficial as predators of household pests like bed bugs, they can deliver a painful defensive bite when mishandled.
Rhagidiidae is a family of soft-bodied, predaceous soil mites in the order Trombidiformes. The family comprises approximately 28 genera and 150 species of whitish mites that inhabit soil environments, with many species showing adaptations to subterranean life. Established by Oudemans in 1922, the family received its modern systematic foundation through Zacharda's 1980 world revision. Many species exhibit troglomorphic traits including reduced eyes, elongated appendages, and depigmentation.
California Darner
Rhionaeschna californica, the California darner, is a medium-sized dragonfly in the family Aeshnidae. Adults are distinguished by bright blue diagonal spots on the abdomen and exhibit sexual dimorphism in coloration and eye color. The species occupies aquatic habitats across western North America and Central America, with larvae requiring several years of aquatic development before nocturnal emergence as adults.
caseless caddisflies
Rhyacophila is a large genus of caddisflies (Trichoptera) in the family Rhyacophilidae, comprising at least 640 described species. The genus is cosmopolitan in distribution, with significant diversity in Europe, Asia, and North America. Larvae are commonly known as 'caseless caddis' because they do not construct portable cases, instead using silk to anchor themselves to substrates in running water. The genus exhibits high endemism in certain regions, with multiple species restricted to specific mountain ranges or islands.
Free-living Caddisflies
Rhyacophilidae is a family of caddisflies (Trichoptera) commonly known as free-living caddisflies. Larvae are distinctive for not constructing portable cases, instead living freely on substrates in freshwater habitats. Most species are predatory. The family contains over 700 described species, with the genus Rhyacophila alone comprising approximately 500 species distributed primarily across the Northern Hemisphere.
Flower Assassin Bugs
Rhynocoris is a genus of assassin bugs in the family Reduviidae, subfamily Harpactorinae. Species occur across Asia, mainland Europe, Africa, and North America. The genus exhibits subsocial behavior with parental care of egg masses, a trait that has evolved independently only six times in Heteroptera. Multiple species have been investigated as biological control agents for agricultural pests, particularly in cotton and other crop systems.
red-legged rove beetle
Rugilus rufipes is a small rove beetle (Staphylinidae) measuring 5–7 mm, distinguished by its dark brown to black body with contrasting red legs and antennae. The species is native to Europe and western Asia, with introduced populations in eastern North America. It inhabits moist terrestrial environments with abundant organic matter and is predatory on small invertebrates.
Saduria entomon is a large benthic isopod crustacean and one of the largest crustaceans in the Baltic Sea, reaching nearly 9 cm in length. It is distributed across Arctic and northern Pacific coasts, the brackish Baltic Sea (where it is a glacial relict), several North European lakes, and has been introduced to the Black Sea. The species is sexually dimorphic with males growing larger and maturing at larger sizes than females. It functions primarily as a predator and scavenger, with documented cannibalism and feeding on other benthic invertebrates.
Saica is a genus of assassin bugs in the family Reduviidae, subfamily Saicinae. These predatory insects inhabit tropical rainforest environments, particularly in the Neotropics. They are characterized by slender bodies, long legs, and distinctive raptorial forelegs adapted for capturing prey. Some species display bright coloration, including brilliant red patterns. The genus is distinguished by a uniquely hooked proboscis tip, an adaptation for subduing prey.
Shore bugs
Saldidae is a family of true bugs (Hemiptera: Heteroptera) commonly known as shore bugs. Adults are small (2–8 mm), oval-shaped insects associated with shoreline habitats. The family comprises approximately 350 described species in 39 genera and 2 subfamilies (Chiloxanthinae and Saldinae), with highest diversity in the Nearctic and Palearctic regions. Members are predators and scavengers, and many species tolerate submergence during high tides. Winter survival occurs through egg or adult diapause.
Common Shore Bug
Saldula saltatoria is a Holarctic shore bug with circumboreal distribution, widespread across central Europe and often occurring in large numbers. It is an active predator of small invertebrates inhabiting diverse shoreline habitats. The species shows remarkable ecological flexibility, occurring from small water bodies to large lakes and rivers, and from sea level to over 2000 meters elevation in alpine regions.
Rusty-tailed Spittlebug-killer
Salpingogaster punctifrons is a rare and elusive syrphid fly known from limited observations in Florida. The species exhibits Batesian mimicry of mud dauber wasps, with distinctive elongated abdominal morphology that sets it apart from typical hoverflies. Its common name references predatory behavior toward spittlebug nymphs.
clown beetle
Saprinus oregonensis is a species of clown beetle in the family Histeridae, first described by LeConte in 1844. The species is distributed across western North America, with records from Canada (Alberta, British Columbia, Manitoba, Saskatchewan), the United States (California, Colorado, New Mexico, Oregon, Washington), and Mexico. As a member of the Saprininae subfamily, it belongs to a group of predatory beetles commonly associated with carrion, dung, and other decomposing organic matter.
Sasajiscymnus is a genus of small lady beetles (Coccinellidae) established by Vandenberg in 2004. The genus contains over 100 species distributed across Asia, Africa, and Oceania. Molecular evidence suggests an origin in the Late Cretaceous, approximately 78 million years ago. The genus includes S. tsugae, which has been widely studied and deployed as a biological control agent against the hemlock woolly adelgid in North America.
Coppery-collared Snail-eating Beetle
Scaphinotus aeneicollis, commonly known as the coppery-collared snail-eating beetle, is a species of ground beetle in the family Carabidae. It is a member of the Carabinae subfamily, which includes large predatory beetles often called 'snail hunters' or 'caterpillar hunters.' The species is restricted to the southern Appalachian region of North America, specifically in coniferous forest habitats in North Carolina. Adults are brachypterous (short-winged) and nocturnal.
Relic Snail-eating Beetle, rilictual snail-eating beetle
Scaphinotus relictus is a species of ground beetle in the family Carabidae, commonly known as the Relic Snail-eating Beetle. This species is found in western North America, with records from Alberta and British Columbia in Canada southward through Idaho, Montana, Washington, and California in the United States. It inhabits deciduous, mixed, and coniferous forest habitats. Adults are brachypterous (short-winged) and nocturnal in their activity patterns.
big-headed ground beetle
Scarites is a genus of large ground beetles in the family Carabidae, containing over 190 described species distributed across the Palearctic, Near East, North America, and North Africa. These beetles are characterized by their disproportionately large heads, prominent mandibles, and elongated, somewhat flattened bodies that superficially resemble tropical stag beetles, though they are not closely related. Both adults and larvae are active predators that hunt soil-dwelling invertebrates. When disturbed, Scarites beetles exhibit thanatosis—folding their legs and arching their backs to feign death.
Scarites marinus is a species of ground beetle in the family Carabidae, described by Nichols in 1986. It belongs to the large genus Scarites, which comprises predatory beetles found in soil and ground-level habitats. The species is documented from coastal and terrestrial regions across the Caribbean Sea, Central America, and North America.
Scarites stenops is a species of ground beetle in the family Carabidae, first described in 2010. Like other members of the genus Scarites, it is a predatory beetle active in soil and ground-level habitats. The species is found in North America, where it contributes to biological control of soil-dwelling pests.
Big-headed Ground Beetle, Pedunculate Ground Beetle, Tunneling Large Ground Beetle
Scarites subterraneus is a large ground beetle in the family Carabidae, commonly known as the big-headed ground beetle. Adults measure 15.0–30.0 mm in length and possess distinctive large mandibles with two teeth, adapted for capturing and consuming prey. The species is native to the Caribbean, Central America, and North America, and has been introduced to Europe. It is primarily nocturnal, spending daylight hours concealed under logs, rocks, soil, and leaf litter. Molecular studies have identified two subspecies: S. subterraneus nebraskensis and S. subterraneus arkansensis.
Large-jawed Pedunculate Ground Beetle
Scarites vicinus is a large ground beetle in the Carabidae family, native to North America. It belongs to the quadriceps group and was previously considered a junior synonym of S. quadriceps but has been revalidated as a distinct species. Phylogenetic analysis of Cox1 genes identifies S. vicinus as the closest relative to S. subterraneus. It is one of two Scarites species recorded from Nebraska.
window fly, House Windowfly
Scenopinus fenestralis, commonly known as the window fly, is a small predatory fly in the family Scenopinidae. Adults are frequently observed resting on windows of old buildings and outhouses, where their behavior appears relatively inactive. The species has been recorded across Europe, including Central Europe and Southern England. Its larvae are notable predators of clothes moth and flea larvae.
Scleropogon cinerascens is a species of robber fly (family Asilidae) described by Back in 1909. Originally described as Stenopogon cinerascens, it was later transferred to the genus Scleropogon. Robber flies are predatory insects known for their robust build, large eyes, and raptorial legs adapted for capturing prey in flight. The specific epithet 'cinerascens' refers to an ash-grey or ashen coloration, likely describing the species' appearance. As with other Asilidae, this species is presumed to be an active aerial predator of other insects.
Giant Centipedes
Scolopendra is a genus of large tropical centipedes in the family Scolopendridae, containing some of the largest living centipedes. The genus was established by Carl Linnaeus in 1758 and remains one of the most species-rich genera in the order Scolopendromorpha. Members are characterized by their substantial size, with the largest species exceeding 30 cm in length, and their potent venom delivered through modified forcipules. The genus exhibits considerable variation in coloration and size across its constituent species.
scorpions
Scorpiones is an ancient order of predatory arachnids, representing the oldest known terrestrial metazoans with fossil records dating back approximately 435 million years. Members are characterized by a pair of large pedipalps modified into grasping pincers, four pairs of walking legs, and a segmented metasoma (tail) terminating in a telson bearing a venomous stinger. Scorpions are the only arachnids that give birth to live young, with females carrying offspring on their backs until their first molt. They exhibit a unique ability to fluoresce under ultraviolet light due to fluorescent compounds in their exoskeletons.
Scotoleon carrizonus is a species of antlion in the family Myrmeleontidae. The genus Scotoleon is found in North America and Central America. Adult males of Scotoleon species frequently have a much longer abdomen tipped with bracket-like claspers. The larvae of Scotoleon species do not construct the trademark pit traps associated with the genus Myrmeleon; instead, they bury themselves just below the soil surface and wait for prey.
Scotoleon dissimilis is a species of antlion in the family Myrmeleontidae. It was first described by Banks in 1903, originally placed in the genus Brachynemurus before being transferred to Scotoleon. The species occurs in Central America and North America. As with other antlions, it undergoes complete metamorphosis with a predatory larval stage and an adult stage.
Scotoleon nigrescens is a species of antlion in the family Myrmeleontidae, order Neuroptera. It was described by Stange in 1970. Antlions in the genus Scotoleon are found in North America, and adults are characterized by their delicate, lacy wings and cryptic coloration that allows them to blend seamlessly against vegetation. The larvae are predatory, living in soil or sand and feeding on small insects.
House Centipede, Thousand-legger
Scutigera coleoptrata, commonly known as the house centipede, is a fast-moving predatory centipede native to the Mediterranean region that has become cosmopolitan through human commerce. Adults possess 15 pairs of extremely long, delicate legs and well-developed faceted eyes—unusual traits among centipedes. They are synanthropic, thriving in human dwellings where they hunt household arthropods. Despite their alarming appearance and speed, they pose minimal threat to humans and are considered beneficial predators of pests.
Ant-like Stone Beetles, Scydmaenines
Scydmaeninae is a subfamily of minute rove beetles (family Staphylinidae) containing approximately 4,500 species in about 80 genera. Formerly treated as a distinct family, they were reclassified as a subfamily in 2009. Members are commonly known as ant-like stone beetles due to their constricted body shape resembling ants. The subfamily has a worldwide distribution and is divided into four extant supertribes: Cephenniitae, Mastigitae, Scydmaenitae, and the extinct fossil supertribe Hapsomelitae.
apicanus lady beetle
Scymnus apicanus is a small lady beetle species described by Chapin in 1973. It belongs to the genus Scymnus, commonly known as dusky lady beetles due to their generally dark coloration. The species is known from North America and has two recognized subspecies: S. a. apicanus and S. a. pseudapicanus. Like other members of its genus, it is presumed to be a predator of small soft-bodied insects, though specific ecological studies are limited.
dusky lady beetle
Scymnus horni is a small lady beetle (family Coccinellidae) first described by Gorham in 1897. It is classified as a 'dusky lady beetle,' a common name applied to several Scymnus species with generally dark or inconspicuous coloration. The species has a notably broad geographic distribution spanning three distinct regions: Central America, North America, and Oceania. Like other members of Scymnus, it is presumed to be a predator of small soft-bodied insects such as aphids and scale insects, though specific prey records for this species are not documented.
dusky lady beetle
Scymnus marginicollis is a species of dusky lady beetle in the family Coccinellidae, first described by Mannerheim in 1843. It is recognized as a member of the subfamily Scymninae, a group of small lady beetles often referred to as 'dusky' or 'scymnine' lady beetles due to their typically dull coloration compared to the brightly colored Coccinellinae. The species is known to occur across North America with two recognized subspecies: S. marginicollis marginicollis and S. marginicollis borealis.
Selenophorus seriatoporus is a Neotropical ground beetle in the family Carabidae. Laboratory studies have demonstrated its predatory capacity and evaluated its life cycle on different substrates. Research has examined dietary effects on its consumption, fecundity, and egg viability, with Tenebrio molitor larvae being the most consumed food source.
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.
dusty-wing
Semidalis is a genus of dusty-wing lacewings (family Coniopterygidae) comprising small predatory insects with bodies covered in white wax. Adults and larvae are active predators of tiny arthropods including spider mites, scale insects, and whiteflies. The genus has an almost cosmopolitan distribution, with records from Europe, China, Africa, and North America. Some species remain active during winter months in temperate regions.
American snail-killing fly
Sepedon americana is a species of marsh fly in the family Sciomyzidae, commonly known as snail-killing flies. The species was described by Steyskal in 1951. Like all members of the genus Sepedon, its larvae are obligate predators of aquatic pulmonate snails. The species occurs in North America and has been documented in regions including Colorado. Adults are active early in the year, with observations in February recorded.