Plastron-respiration
Guides
Ancyronyx
spider water beetles, spider riffle beetles
Ancyronyx is a genus of aquatic riffle beetles in the family Elmidae, commonly known as spider water beetles or spider riffle beetles. The genus comprises 21 described species distributed across North America, South Asia, China, and Southeast Asia, with the Philippines recognized as a center of diversity containing 11 endemic species. Members are obligate inhabitants of lotic freshwater environments, where both adults and larvae cling to submerged substrates using their elongated legs and strong claws. The genus is notable for its potential use as a bioindicator of water quality due to its sensitivity to pollution and oxygen levels.
Ancyronyx variegata
Spider Water Beetle
Ancyronyx variegata is a riffle beetle (Elmidae) commonly known as a Spider Water Beetle, characterized by extremely long legs and often a cross-like elytral color pattern that gives it a spider-like appearance. It inhabits clean, pristine running waters in lotic environments and has been studied for its life history and energetics in Northwest Arkansas and Southeast Texas. The species exhibits a univoltine life cycle with adults present year-round.
Elmidae
Riffle beetles
Elmidae, commonly known as riffle beetles, is a family of aquatic beetles in the superfamily Byrrhoidea containing over 150 genera and 1,500 described species. Both adults and larvae are primarily aquatic, inhabiting fast-flowing shallow areas of streams and rivers such as riffles. Adults breathe underwater using a plastron—a microfilm of air held by microscopic hairs on their body surface that enables oxygen diffusion from the water. The family has significant value in freshwater biomonitoring due to their sensitivity to water pollution.
Elmini
riffle beetles
Elmini is a tribe of riffle beetles within the family Elmidae, comprising over 90 genera and approximately 1,200 described species in North America. These beetles are strictly aquatic as adults and larvae, inhabiting flowing water systems. The tribe represents a major radiation within the Elmidae, with species diversity concentrated in freshwater habitats.
Heterelmis glabra
riffle beetle
Heterelmis glabra is a species of riffle beetle in the family Elmidae, found in Central America and North America. The largest known populations occur in springs associated with the upper Devils River in south-central Texas. As a spring-adapted organism, it has life-history patterns requiring surface habitat components, making it vulnerable to changes in spring flow. The species has been studied using N-mixture models to assess abundance and distribution across spring sources.
Heterelmis obscura
Heterelmis obscura is a species of riffle beetle in the family Elmidae, first described by Sharp in 1882. It inhabits freshwater environments in Central and South America. Like other elmid beetles, it is fully aquatic throughout its life cycle, with adults possessing a plastron—a layer of air trapped by body hairs that enables underwater respiration.
Heterelmis vulnerata
riffle beetle
Heterelmis vulnerata is a species of riffle beetle in the family Elmidae, first described by LeConte in 1874. It is distributed across Central America and North America. Riffle beetles are aquatic insects that inhabit fast-flowing, oxygen-rich waters where they spend their entire life cycle submerged. Adults possess a plastron—a layer of air trapped by body hairs that allows them to breathe underwater without surfacing.
Naucoridae
creeping water bugs, saucer bugs
Naucoridae is a family of aquatic predatory true bugs comprising approximately 400 species in 46 genera across five subfamilies. Members are commonly known as creeping water bugs or saucer bugs due to their dorsoventrally flattened, oval body shape. They inhabit freshwater environments worldwide with greatest diversity in tropical regions, ranging from still waters to torrential streams. Most species are lotic, occurring in flowing waters rather than lentic habitats. They are predatory, feeding on other small invertebrates using piercing-sucking mouthparts.
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.
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.