Beetles are insects that form the order Coleoptera, in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 described species, is the largest of all orders, constituting almost 40% of described insects and 25% of all known animal species; new species are discovered frequently, with estimates suggesting that there are between 0.9 and 2.1 million total species. Found in almost every habitat except the sea and the polar regions, they interact with their ecosystems in several ways: beetles often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are serious agricultural pests, such as the Colorado potato beetle, while others such as Coccinellidae eat aphids, scale insects, thrips, and other plant-sucking insects that damage crops.
Spercheus is a genus of aquatic beetles which are placed in a family of their own, Spercheidae within the Hydrophiloidea. About 20 species are known from around the world except the Nearctic with the majority being from the Oriental and Afrotropical Realms.
The whirligig beetles are water beetles, comprising the family Gyrinidae that usually swim on the surface of the water if undisturbed, though they swim underwater when threatened. They get their common name from their habit of swimming rapidly in circles when alarmed, and are also notable for their divided eyes which are believed to enable them to see both above and below water. The family includes some 700 extant species worldwide, in 15 genera, plus a few fossil species. Most species are very similar in general appearance, though they vary in size from perhaps 3 mm to 18 mm in length. They tend to be flattened and rounded in cross section, in plain view as seen from above, and in longitudinal section. In fact their shape is a good first approximation to an ellipsoid, with legs and other appendages fitting closely into a streamlined surface. Whirligig beetles belong to the beetle suborder Adephaga, which also includes ground beetles and diving beetles.
A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. There are approximately 2000 species of true water beetles native to lands throughout the world.
Sphaerius is a genus of beetles in the family Sphaeriusidae, comprising 18 species. It is one of the two extant genera in the family, the other being Bezesporum. They are typically found along the edges of streams and rivers, where they feed on algae; they occur on all continents except Antarctica. Three species occur in the United States.
Myxophaga is the second-smallest suborder of the Coleoptera after Archostemata, consisting of roughly 65 species of small to minute beetles in four families. The members of this suborder are aquatic and semiaquatic, and feed on algae.
Yara is a genus of beetles in the family Hydroscaphidae, from South America and Central America. Containing five species:
Nosodendridae is a family of beetles, with less than a hundred species in three extant genera, which are found worldwide. Nosodendron, the largest genus, is found in forests and attracted to yeast generated slime on the wounds of trees, and likely consumes fermented substances as well as fungi and microorganisms. Several additional genera and species are known from the fossil record. Nosodendridae is considered to be an isolated lineage within Polyphaga, being the sister group to the clade containing Staphyliniformia, Bostrichoidea and Cucujiformia.
Incoltorrida is a genus of myxophagan water beetles from Madagascar in the family Torridincolidae.
Ancyronyx, commonly known as spider water beetles or spider riffle beetles, is a genus of aquatic riffle beetles from North America, South Asia, China, and Southeast Asia. They are small beetles with extremely long legs ending in strong claws. Both the adults and the larvae are found underwater in the shallow riffles of streams and rivers, clinging to rocks or submerged wood. They feed on algae and decaying wood tissue. The genus contains twenty-one species, eleven of which are endemic to the Philippines.
Acidocerinae is a subfamily in the family Hydrophilidae of aquatic beetles, and it contains over 500 species in 23 genera.
Gyrininae is a subfamily of ground and water beetles in the family Gyrinidae. There are at least 740 described extant species in Gyrininae.
Saprininae is a subfamily of clown beetles in the family Histeridae. There are more than 50 genera and 800 described species in Saprininae.
Nosodendron is a genus of wounded-tree beetles in the family Nosodendridae. There are more than 70 described species in Nosodendron.
Hydroscapha natans is a species of skiff beetle in the family Hydroscaphidae. It is found in North America.
Epimetopidae is a family of semi-aquatic beetles belonging to the Hydrophiloidea. They are found in sand and gravel at the edges of streams, rivers and shallow freshwater ponds. These beetles are shorter than half a centimeter long and have a pronotum with a central projection forming a shelf above the head. On the underside of the abdomen only four sternites are visible. There are approximately 72 described species in three genera, Epimetopus which is restricted to the New World, mostly Neotropical, Eupotemus with two Afrotropical species and Eumetopus with some Oriental species. Females carry their eggcases on the underside of the abdomen. The larvae are probably carnivorous based on their mouthparts and likely live in the same habitats as the adults.
Hydroscapha jaechi, is a species of skiff beetle endemic to Sri Lanka.
Hydroscapha monticola, is a species of skiff beetle native to India and Sri Lanka.
Anoplognathus olivieri is a species of beetle within the genus Anoplognathus.
