Nearctic
Guides
Semioscopis
Semioscopis is a genus of small moths in the family Depressariidae, comprising approximately 14 valid species distributed across the Palearctic and Nearctic regions. The genus was established by Hübner in 1825 and is currently classified in the subfamily Depressariinae. Species are distinguished primarily by genitalia morphology and grouped into seven species-level clades based on phylogenetic analysis of COI gene sequences. A new species, S. sinicella, was described in 2025 from montane habitat in central China.
Semium
Semium is a genus of plant bugs in the family Miridae, tribe Semiini, subfamily Phylinae. The genus contains seven described species distributed across North America from Canada to Mexico. One species, Semium brailovskyi, has been documented in association with the host plant Euphorbia misera (Euphorbiaceae). The genus was established by Reuter in 1876.
Senopterina foxleei
signal fly
Senopterina foxleei is a species of signal fly in the family Platystomatidae, first described by Shewell in 1962. Signal flies are characterized by their distinctive wing patterns and behaviors involving wing signaling. The species is part of a genus distributed primarily in the Nearctic region. Observations suggest it is an active, diurnal fly often found in wooded or forested habitats.
Sepedon tenuicornis
marsh fly
Sepedon tenuicornis is a species of marsh fly in the family Sciomyzidae, first described by Cresson in 1920. Like other members of the genus Sepedon, this species has aquatic predatory larvae that feed on pulmonate snails. The genus comprises approximately 20 recognized species in North America, arranged into species groups based on shared morphological characteristics. Adults are slender flies with elongated bodies, concave faces, and prominent antennae.
Sepedophilus marshami
A small rove beetle in the subfamily Tachyporinae. Native to the Palearctic region, with documented introduction to eastern North America. First recorded in the Nearctic region from Canada (New Brunswick, Nova Scotia, Ontario, Quebec) and the United States (New Hampshire).
Serica anthracina
Serica anthracina is a small scarab beetle in the family Scarabaeidae, described by LeConte in 1856. Adults measure 5–8.5 mm in length and exhibit variable coloration ranging from uniform testaceous to black. The species is distributed across western North America, from the Canadian prairies through the Rocky Mountain region to the Pacific coast.
Serica atracapilla
Serica atracapilla is a small scarab beetle in the family Scarabaeidae, distributed across eastern and central North America. Adults measure approximately 10 mm in length and are characterized by their chestnut-brown coloration and polished, shining upper surface lacking any silky or pruinose luster. The species has been recorded from 19 U.S. states and 7 Canadian provinces, indicating a broad geographic range within the Nearctic region.
Serica elusa
Serica elusa is a small scarab beetle in the family Scarabaeidae, first described by Dawson in 1919. Adults measure approximately 10 mm in length and are characterized by their chestnut-brown coloration with a polished, shining upper surface lacking any sericeous or pruinose luster. The species is restricted to the northeastern Nearctic region, occurring in parts of Canada and the northeastern United States.
Serica howdeni
Serica howdeni is a small scarab beetle described by Dawson in 1967. Adults measure approximately 8 mm in length and are characterized by a dark brown, glabrous, and shining exosurface densely covered with moderate-sized punctures. The species is known only from Texas in the southern United States.
Serica opposita
Serica opposita is a small scarab beetle in the family Scarabaeidae, first described by Dawson in 1921. Adults reach approximately 8 mm in length and are very similar in appearance to the congeneric species Serica spicula, though slightly larger. The species is distributed across the eastern and central United States.
Serica tristis
May beetle, Junebug
Serica tristis is a small scarab beetle in the family Scarabaeidae, commonly known as a May beetle or Junebug. Adults measure 7–8.5 mm and display variable coloration from chestnut to nearly black with a metallic iridescent sheen. The species is distributed across northeastern North America, with records from multiple Canadian provinces and adjacent U.S. states.
Sericophanes heidemanni
Sericophanes heidemanni is a species of plant bug in the family Miridae, first described by Poppius in 1914. It belongs to the genus Sericophanes, a group within the diverse mirid fauna of North America. The species has been documented in the eastern United States, with confirmed records from Georgia and New York.
Setodius
Setodius is a genus of scarab beetles in the family Scarabaeidae, subfamily Aphodiinae. It was established by Gordon and Skelley in 2007 and belongs to the tribe Aphodiini. The genus is known from the Nearctic region. As a member of Aphodiinae, it is part of a diverse group of dung beetles, though specific ecological details for this genus remain poorly documented.
Shipsa
spring stoneflies
Shipsa is a monotypic genus of spring stoneflies in the family Nemouridae, containing the single species Shipsa rotunda. The genus was described by Ricker in 1952. The sole species has an extensive Nearctic distribution across northern North America, with records from multiple Canadian provinces and US states. Morphological studies indicate little variation in reproductive structures across its wide geographic range.
Shipsa rotunda
Intrepid Forestfly
Shipsa rotunda is a Nearctic stonefly species in the family Nemouridae with an extensive distribution across Canada and the United States. Despite its wide geographic range, the species exhibits remarkably little morphological variation in both males and females. Reproductive terminalia have been examined using scanning electron microscopy from specimens across its range, revealing consistent structural features. The species was originally described as Nemoura rotunda by Claassen in 1923 and later transferred to the genus Shipsa.
Silinae
soldier beetles
Silinae is a subfamily of soldier beetles (family Cantharidae) comprising approximately 6 genera and more than 180 described species. The subfamily includes the genera Silis, Polemius, Discodon, Plectonotum, Ditemnus, and Tytthonyx. Species occur across the Nearctic and Neotropical regions, with some lineages showing remarkable high-altitude adaptations including extreme brachelytry (shortened elytra) and wing reduction.
Silusa
Silusa is a genus of rove beetles (Staphylinidae: Aleocharinae: Homalotini) established by Erichson in 1837. The genus occurs in the Nearctic and Palearctic regions, with species documented in Europe and North America. Nearctic species have been subject to recent taxonomic revision, which expanded known distributions and clarified species boundaries through examination of external and genital morphology.
Silusa densa
Silusa densa is a rove beetle in the family Staphylinidae, subfamily Aleocharinae. Originally described from California in 1909, the species was later documented in Alberta, Canada, representing a significant range expansion and first Canadian record. As a member of the genus Silusa, it belongs to a group of small, often overlooked beetles that are part of the diverse rove beetle fauna of North America.
Simophion excarinatus
Simophion excarinatus is a species of ichneumon wasp in the family Ichneumonidae, described by Cushman in 1947. The genus Simophion is a relatively small group within the diverse ichneumonid fauna. This species is part of the parasitoid wasp fauna that plays important roles in regulating insect populations. Available records indicate it has been documented in field observations, though detailed biological studies remain limited.
Simplocaria semistriata
pill beetle
Simplocaria semistriata is a species of pill beetle in the family Byrrhidae, first described by Fabricius in 1794. It is one of approximately 30 species in the genus Simplocaria. The species has been recorded across a broad geographic range spanning Europe, Northern Asia (excluding China), and North America. Pill beetles in this family are known for their ability to conglobate—roll into a ball—and often inhabit moist, mossy environments.
Siphlonurus columbianus
Columbian gray drake
Siphlonurus columbianus is a species of mayfly in the family Siphlonuridae, described by James Halliday McDunnough in 1925. It is native to the Nearctic region and is one of several Siphlonurus species known to fly fishermen as "gray drakes." Adults are medium-sized mayflies with distinctive body segmentation. Like other members of its genus, it has a two-winged adult stage and an aquatic nymphal stage. The species is occasionally referenced in angling literature, though detailed biological studies appear limited.
Siphlonurus phyllis
primitive minnow mayfly
Siphlonurus phyllis is a species of primitive minnow mayfly in the family Siphlonuridae. It was described by McDunnough in 1923. The species is distributed across all of Canada and the northern United States.
Siphlonurus quebecensis
early brown quill mayfly, gray drake
Siphlonurus quebecensis is a species of primitive minnow mayfly in the family Siphlonuridae. It occurs in North America and is known to anglers as the 'early brown quill' or 'gray drake,' a name reflected in fly-fishing patterns designed to imitate its adult form. The species is part of a group of mayflies whose aquatic nymphs and winged adults serve as important prey for trout and other sport fish.
Siphlonurus rapidus
Siphlonurus rapidus is a species of primitive minnow mayfly in the family Siphlonuridae. It was described by McDunnough in 1924. The species is found in North America. Like other members of the genus Siphlonurus, it is considered a "gray drake" mayfly of interest to fly fishermen.
Siphlonurus spectabilis
primitive minnow mayfly
Siphlonurus spectabilis is a species of primitive mayfly in the family Siphlonuridae, first described by Traver in 1934. It belongs to a group commonly known as minnow mayflies, characterized by their relatively primitive morphological features compared to other mayfly families. The species has a documented distribution in northern Canada and the western United States.
Sironidae
Sironid Harvestmen
Sironidae is a family of Cyphophthalmi harvestmen comprising more than 60 described species. It was the first described family of the suborder Cyphophthalmi and remains among the least understood phylogenetically. The family exhibits a predominantly Laurasian distribution, with species concentrated in temperate Europe and the west coast of North America. Monophyly of the family is poorly supported with traditional molecular markers; the Mediterranean genus Parasiro and Japanese genus Suzukielus sometimes branch basally relative to other sironids.
Sisyra apicalis
spongillafly
Sisyra apicalis is a species of spongillafly in the family Sisyridae, first described by Banks in 1908. Spongillflies are a small family of aquatic insects with specialized larval biology tied to freshwater sponges. The species has a broad Neotropical and Nearctic distribution, spanning from North America through Central America and the Caribbean to South America, with documented records across Brazil including the semiarid Caatinga biome.
Slaterocoris atritibialis
Slaterocoris atritibialis is a species of plant bug in the family Miridae. It was described by Knight in 1938. The species is known from scattered records across eastern North America, with documented occurrences in Ontario, New York, West Virginia, and Georgia.
Smiliinae
Smiliinae is a large subfamily of treehoppers (Membracidae) comprising approximately 100 genera organized into 10 tribes, with the majority of diversity concentrated in the Americas. The subfamily includes approximately 140 described species, though this likely underrepresents true diversity. Members are characterized by elaborate pronotal modifications that produce bizarre shapes including thorn-like projections, ant-mimicking forms, and other structures whose functions remain incompletely understood. The nominotypical tribe Smiliini contains 169 species in 23 genera and is predominantly Nearctic in distribution, with evolutionary origins traced to Central America and Mexico followed by multiple dispersals to temperate North America.
Smiliini
Smiliini is a tribe of treehoppers in the family Membracidae, subfamily Smiliinae, containing approximately 6 genera and at least 40 described species. Members are predominantly Nearctic in distribution and primarily feed on trees, with many species associated with oak (Quercus). The tribe was historically defined broadly to include Telamonini, but phylogenetic analysis has reinstated Telamonini as a separate tribe, narrowing the definition of Smiliini. Several genera within Smiliini, including Atymna, Cyrtolobus, Heliria, and Telamona, are not monophyletic.
Sonia
Sonia is a genus of tortricid moths in the family Tortricidae, subfamily Olethreutinae, and tribe Eucosmini. The genus was established by Heinrich in 1923. Like other olethreutine tortricids, species in this genus are small to medium-sized moths with characteristic wing patterns and larval stages that typically develop within plant tissues such as stems, roots, or fruits.
Sonorarctia
Sonorarctia is a genus of tiger moths in the family Erebidae, established by Ferguson in 1985. The genus contains two described species: S. fervida (Walker, 1855) and S. nundar (Dyar, 1907). Both species were originally described under other genera and later transferred to Sonorarctia. The genus is part of the Arctiinae subfamily, a diverse group of moths commonly known as tiger moths.
Sophona snellingi
Sophona snellingi is a clearwing moth in the family Sesiidae, described by Eichlin in 1986. It belongs to the subfamily Tinthiinae, a group of relatively small and poorly known sesiid moths. The species is named in honor of entomologist Roy R. Snelling. Like other members of its family, it is presumed to exhibit wasp-mimicry through transparent wings and a slender body form.
Soyedina
Soyedina is a genus of small stoneflies in the family Nemouridae, endemic to the Nearctic region. The genus was originally described as a subgenus of Nemoura by Ricker in 1952 and elevated to full genus status by Illies in 1966. It currently contains 11 described species, many of which are difficult to distinguish without examination of male genitalia. Species are distributed across North America from the Appalachian Highlands to western North America.
Spathilepia
Falcate Skipper
Spathilepia is a monotypic genus of skippers in the family Hesperiidae, subfamily Eudaminae. The sole species, Spathilepia clonius, is known as the Falcate Skipper. The genus was established by Arthur Gardiner Butler in 1870. It is distributed from the southern United States through Central America and into South America.
Spathilepia clonius
Falcate Skipper
Spathilepia clonius, commonly known as the Falcate Skipper, is the sole species in the monotypic genus Spathilepia within the skipper family Hesperiidae. This butterfly ranges from the southern United States through Central America and into South America as far as Argentina. It is a member of the subfamily Eudaminae, a group characterized by their robust bodies and rapid, darting flight patterns. The species has been documented across diverse tropical and subtropical habitats.
Sphaeropthalma pensylvanica
velvet ant
Sphaeropthalma pensylvanica is a velvet ant (family Mutillidae), a group of solitary wasps known for their striking aposematic coloration and painful sting. The species exhibits notable sexual dimorphism: females are wingless and resemble ants, while males possess wings. It has been documented as a parasitoid of mud dauber wasps, particularly developing within cocoons of the organ pipe mud dauber (Trypoxylon politum). Research has revealed unusual reproductive characteristics including facultative size-dependent sex allocation, where larger females produce proportionally more female offspring. The species is also notable for phoretic copulation, a mating behavior in which the male transports the female by flight or foot from the initial contact site before mating occurs.
Sphaeropthalma pensylvanica pensylvanica
velvet ant
A velvet ant subspecies in the family Mutillidae, notable for being the first record of phoretic copulation in the subfamily Sphaeropthalminae. Males transport females by flight and/or foot from the initial contact site before mating occurs. The species is a solitary parasitoid with unusual sex allocation patterns and has been reared from cocoons of the organ pipe mud dauber (Trypoxylon politum).
Sphaeropthalma unicolor
Sphaeropthalma unicolor is a velvet ant species (family Mutillidae) native to Mediterranean regions of the Nearctic. It belongs to a species-complex that includes desert-adapted relatives, with phylogenetic studies indicating diversification driven by Pleistocene climatic fluctuations. The species shows little population-level genetic structuring across its range.
Sphragisticus nebulosus
dirt-colored seed bug
Sphragisticus nebulosus is a species of true bug in the family Rhyparochromidae, commonly known as dirt-colored seed bugs. It has a broad distribution spanning North America, Europe, and Asia. The species was first described by Fallén in 1807 under the name Lygaeus nebulosus. Like other members of its family, it is associated with seeds and ground-level vegetation.
Spinadis simplex
Wallace's Deepwater Mayfly
Spinadis simplex is a species of mayfly in the family Heptageniidae, commonly known as Wallace's Deepwater Mayfly. It is a North American species first described by Walsh in 1863. The genus Spinadis is distinguished within the Heptageniidae by specific morphological characteristics related to wing venation and genitalia structure. Like other members of the family, S. simplex has aquatic nymphal stages and winged adult stages with brief adult lifespans.
Spodoptera dolichos
Sweet Potato Armyworm Moth, Dolichos Armyworm Moth, Sweetpotato Armyworm Moth
Spodoptera dolichos is a noctuid moth species native to the Americas, ranging from the southern United States through Central America to Argentina. The species was first described by Johan Christian Fabricius in 1794. Adults have a wingspan of approximately 40 mm. Larvae are polyphagous, feeding on a wide variety of wild and cultivated plants.
Steffanolampus
Steffanolampus is a monotypic genus of chalcidoid wasps established by Peck in 1974 to accommodate Perilampus salicetum Steffan. The single species has a Nearctic distribution, with records from eastern Canada and the United States extending from Quebec to Maryland and Michigan, plus an isolated western population in Washington State. It is associated with anobiid beetles, though the precise nature of this relationship remains unspecified.
Stegea
Stegea is a genus of moths in the family Crambidae, subfamily Glaphyriinae. The genus was erected by Munroe in 1964 and contains approximately eleven described species distributed across North America, the Caribbean, and Central America. Species within this genus are generally small moths with relatively simple wing patterns.
Stemmops
Stemmops is a genus of small comb-footed spiders (Theridiidae: Spintharinae) first described in 1894. The genus contains approximately 27 species, with the majority distributed in the Americas from the United States through Central America to Brazil, and a smaller number of species in East Asia including China, Japan, Korea, and Laos. One species, S. satpudaensis, has been recorded from India.
Stenacidia violacea
Stenacidia violacea is a springtail species in the family Sminthurididae, characterized by distinctive coloration with yellowish body and purple lateral markings. The species exhibits sexual dimorphism in coloration, with females sometimes appearing dark purple. A notable behavioral trait involves antenna contact during mating, described as resembling a 'kiss'. The species has a broad distribution spanning the Nearctic and Palearctic regions, with a recent range extension to Iran documented in 2019.
Stenacron floridense
Stenacron floridense is a species of flatheaded mayfly in the family Heptageniidae, first described by Lewis in 1974. It is part of a genus of mayflies characterized by dorsoventrally flattened bodies adapted for clinging to substrates in flowing water. The species is recorded from North America, though specific details about its biology remain limited in published literature.
Stenelmis occidentalis
Neararctic Riffle Beetle
Stenelmis occidentalis is a species of riffle beetle in the family Elmidae, described by Schmude and Brown in 1991. Riffle beetles are aquatic insects adapted to life in fast-flowing freshwater habitats. The species is found in both Central America and North America, reflecting a transcontinental distribution across the Nearctic region.
Stenobarichneumon saundersii
Stenobarichneumon saundersii is a species of ichneumon wasp in the family Ichneumonidae. It was described by Ezra Townsend Cresson in 1877. The genus Stenobarichneumon is a small group within the diverse ichneumonid fauna. Very few observations of this species exist in public databases.
Stenochidus
Stenochidus is a genus of darkling beetles (family Tenebrionidae) established by LeConte in 1862. The genus is native to the Nearctic region. As with many tenebrionid genera, species within Stenochidus are generally associated with arid or semi-arid environments. The genus is represented by a modest number of observations, suggesting either restricted distribution, cryptic habits, or limited survey effort.