Semi-aquatic
Guides
Axymyia furcata
Axymyia furcata is a xylophilic, semi-aquatic nematoceran fly and the sole described species in the genus Axymyia. Once considered rare, the species has been documented across twenty U.S. states and two Canadian provinces in the eastern Nearctic. Its larvae develop in water-filled rot holes and cavities of living hardwood trees within deciduous forests. Research indicates post-glacial range expansion from southern Appalachian refugia, with possible survival in northern refugia including the Driftless area and southeastern Ohio.
Axymyiidae
A small family of nematoceran flies comprising four extant genera and nine described species, with eight additional fossil species. Axymyiidae is the sole member of the infraorder Axymyiomorpha, though historically classified within Bibionomorpha. The family is distributed across the Holarctic and Oriental regions. Larvae are xylophilic and semi-aquatic, developing in saturated decaying wood.
Bagous
Bagous is a genus of semi-aquatic weevils in the family Curculionidae containing at least 360 described species. Many species are associated with aquatic or semi-aquatic habitats, with several species developed as biological control agents for invasive aquatic plants, particularly Hydrilla verticillata. The genus includes both native and introduced species with varying degrees of host specificity. Larvae typically develop within plant stems while adults feed on stems and leaves.
Dolichopus albiciliatus
Dolichopus albiciliatus is a species of long-legged fly in the family Dolichopodidae, first described by Loew in 1862. Members of the genus Dolichopus are characterized by elongated legs and often metallic coloration. As with other dolichopodids, adults are predatory on small insects.
Dolomedes albineus
white-banded fishing spider, whitebanded fishing spider
Dolomedes albineus is a large nursery web spider native to the southeastern and central United States. Mature females reach approximately 23 mm in body length, males about 18 mm. The species is named for the distinctive white band immediately below the eyes and above the chelicerae, though coloration is highly variable—ranging from mottled gray to mossy green with darker markings. Unlike some fishing spiders, D. albineus is strongly associated with aquatic habitats, particularly cypress swamps and river edges, where it hunts from perches on vegetation or pilings. Females carry egg sacs in their jaws before constructing nursery webs and guarding the emerging spiderlings.
Dolomedes scriptus
striped fishing spider
Dolomedes scriptus, the striped fishing spider, is a large semi-aquatic hunting spider native to North America. Females can exceed 6 cm in legspan. The species is distinguished by pale brown coloration with lighter stripes on the legs and a longitudinal stripe along each side of the body. It is closely related to D. tenebrosus and shares the genus's characteristic ability to hunt on and near water surfaces.
Epimetopidae
Hooded Shore Beetles
Epimetopidae is a small family of semi-aquatic beetles in the superfamily Hydrophiloidea, comprising approximately 72 described species across three genera. The family exhibits a disjunct distribution: Epimetopus is restricted to the New World (Neotropical and Nearctic regions), Eumetopus occurs in Asia, and Eupotemus is found in Africa. A distinctive feature of the family is the pronotal hood—a central projection of the pronotum that forms a shelf above the head. Females of all three genera carry egg cases on the underside of the abdomen, representing one of three independent origins of maternal care in Hydrophiloidea.
Erodiscini
Erodiscini is a tribe of weevils within the subfamily Curculioninae (Curculionidae), containing semi-aquatic species such as Ludovix fasciatus. The tribe includes the genus Sicoderus, which is diverse in the West Indies with over 75 described species. At least some members exhibit specialized surface swimming behavior using all three pairs of legs in a coordinated breast stroke-like motion.
Hydroisotoma
Hydroisotoma is a genus of springtails in the family Isotomidae, established by Stach in 1947. The genus includes species found in aquatic or semi-aquatic environments, with Hydroisotoma schaefferi documented from the eastern United States. Members of this genus belong to the diverse order Entomobryomorpha, which contains many of the larger and more active springtail species.
Hydrophorus aestuum
Hydrophorus aestuum is a species of long-legged fly in the family Dolichopodidae. Like other members of the genus Hydrophorus, it is adapted to semi-aquatic environments where it skates across water surfaces. The species was described by Loew in 1869. Adults are predatory on small insects and other invertebrates, including mosquito larvae.
Leptysminae
spur-throat toothpick grasshoppers
Leptysminae is a subfamily of grasshoppers in the family Acrididae, commonly known as spur-throat toothpick grasshoppers. The subfamily contains at least 20 genera distributed across North, Central, and South America. Members are characterized by slender, elongate bodies and association with aquatic or semi-aquatic habitats. The genus Cornops, a well-studied member, has been investigated for biological control of invasive water hyacinth.
Neolimnophila placida
Placid Crane Fly
Neolimnophila placida is a crane fly species in the family Limoniidae, subfamily Chioneinae. It is widely distributed across the Holarctic region, occurring in both the Nearctic and Palaearctic realms. The species has been documented from northern North America through much of Europe and across northern Asia to Japan. Like other limoniid crane flies, it is associated with moist habitats where larvae develop in decaying organic matter.
Ochteridae
Velvety Shore Bugs
Ochteridae is a small family of true bugs (Hemiptera: Heteroptera: Nepomorpha) comprising approximately 80–90 described species in eight genera. Commonly known as velvety shore bugs, they are semi-aquatic insects inhabiting the margins of freshwater bodies worldwide, with highest diversity in tropical regions. The family is characterized by a velvety body texture, small size (4.5–9 mm), and distinctive antennal and leg sensilla adapted to riparian habitats. Recent taxonomic revisions have significantly expanded the known species diversity, particularly in Australia, Mesoamerica, and the Andes.
Pachyceramyia
Pachyceramyia is a genus of muscid flies established by Albuquerque in 1955. The genus contains approximately six described species distributed primarily in the Americas. Species are classified within the subfamily Coenosiinae and tribe Limnophorini, a group associated with semi-aquatic and shoreline habitats. The genus name derives from Greek roots suggesting thick or swollen horn-like structures, likely referring to distinctive antennal or facial features.
Parauleutes nebulosus
Nebulous weevil
Parauleutes nebulosus is a small weevil species in the family Curculionidae, subfamily Bagoinae. The species was originally described by LeConte in 1876 under the genus Bagous, and is now classified in the genus Parauleutes. It is known from scattered records across northern North America, including the Canadian provinces of Alberta, British Columbia, New Brunswick, and Saskatchewan. The specific epithet "nebulosus" (Latin for "cloudy" or "foggy") likely refers to a mottled or indistinct color pattern on the body.
Paroxya atlantica
Atlantic Grasshopper, Atlantic Locust
Paroxya atlantica is a species of spur-throated grasshopper in the family Acrididae. It is native to North America, with documented occurrence in Florida. The species exhibits semi-aquatic habits, frequently associated with vegetation at the margins of slow-moving water bodies. A 2011 study in Behavioral Ecology examined how limb autotomy affects its escape behavior.
Peltodytes festivus
Peltodytes festivus is a species of crawling water beetle in the family Haliplidae. It occurs in North America. Members of this family are semi-aquatic, inhabiting the margins of ponds, lakes, and slow-moving streams where they feed on algae and detritus. The genus Peltodytes is distinguished from other haliplid genera by morphological features of the elytra and hind legs.
Petrophila confusalis
confusing petrophila moth
Petrophila confusalis is a semi-aquatic moth in the family Crambidae, commonly known as the confusing petrophila moth. Adults are small, with forewing lengths of 5–11 mm, and are active from April to September. The species is notable for its specialized aquatic larval stage, during which caterpillars feed on algae and diatoms in fast-moving streams. The moth serves as a host for the parasitic aquatic wasp Tanychela pilosa and has been observed in large grazing zones that contribute to epilithic spatial patchiness. In 2021, it was listed on the Nevada Division of Natural Heritage watch list due to population decline.
Piratula cantralli
Cantrall's Wolf Spider
Piratula cantralli is a species of wolf spider in the family Lycosidae, originally described as Pirata cantralli by Wallace and Exline in 1978. The species is known from the northern United States and Canada, with records from Alberta and Manitoba. It belongs to the genus Piratula, which comprises semi-aquatic wolf spiders often found in association with wetlands and riparian habitats. This species is rarely recorded, with only six observations documented on iNaturalist.
Pisauridae
Nursery Web Spiders, Fishing Spiders
Pisauridae is a moderately diverse family of hunting spiders comprising approximately 333 described species worldwide. Members exhibit exceptional behavioral diversity, ranging from web-based hunters and water surface hunters to ambush hunters in vegetation. The family is best known for the distinctive 'nursery web' behavior: females carry egg sacs with their jaws and pedipalps (not spinnerets), then construct protective silk tents for emerging spiderlings, which they guard until dispersal. The European species Pisaura mirabilis is the namesake 'nursery web spider,' though the family includes fishing spiders (Dolomedes), semi-aquatic specialists, and strictly terrestrial forms.
Plateumaris flavipes
Flavous-footed reed beetle
Plateumaris flavipes is a leaf beetle in the subfamily Donaciinae, commonly known as reed beetles. Members of this subfamily are semi-aquatic, typically associated with emergent vegetation in freshwater habitats. The species is recorded from western and northern North America, including Alberta, British Columbia, and Labrador in Canada. Available sources provide limited specific ecological detail for this species.
Rhagovelia distincta
smaller water strider
Rhagovelia distincta is a species of smaller water strider in the family Veliidae. It inhabits freshwater surface habitats across Central America and North America. As a member of the genus Rhagovelia, it belongs to a group of semi-aquatic true bugs adapted for life on the water surface.
Saldula andrei
Saldula andrei is a species of shore bug in the family Saldidae, described by Drake in 1949. It belongs to the genus Saldula, a diverse group of predatory true bugs commonly found in moist shoreline habitats. The species is recorded from Middle America and North America. Like other saldid bugs, it is likely adapted to semi-aquatic environments where it preys on small invertebrates.
Stenelmis
riffle beetle
Stenelmis is the largest and most widespread genus of beetles in the family Elmidae. Members are commonly known as riffle beetles due to their association with fast-flowing stream habitats. The genus contains numerous species distributed across multiple continents, with documented presence in North America, Europe, and the Caucasus region.
Stenus colon
Stenus colon is a species of rove beetle in the family Staphylinidae, commonly referred to as a water skater due to its association with moist habitats. It was described by Thomas Say in 1831 and occurs across eastern and central North America. The species belongs to the large genus Stenus, which contains over 3,000 described species worldwide, many of which are semi-aquatic or inhabit wet environments.
Trechalea
Trechalea is a genus of semi-aquatic spiders in the family Trechaleidae, distributed from the southern United States through Central and South America to northern Argentina. The genus was established by Thorell in 1869, replacing the preoccupied name Triclaria. At least one species, T. extensa, exhibits specialized diving behavior as an antipredator tactic, using plastron respiration to remain submerged for over 30 minutes.
Unnamed-near-cyphon obscurus
Unnamed-near-cyphon obscurus refers to an undescribed species closely related to Cyphon obscurus within the family Scirtidae (marsh beetles). These beetles are small, semi-aquatic insects associated with moist environments. The 'unnamed-near-' designation indicates a distinct but closely related taxon that has not yet received formal scientific description. Members of this group are characterized by their compact body form and association with wet habitats.