More than 20 species of twigs live in Russia , most of them belong to the genus of true twigs ( Gyrinus ).
The body shape of adult beetles is teardrop-shaped or spindle-shaped [4] . Body length up to 8 millimeters.
A head with two pairs of eyes: the upper for the air, located on the forehead, and the lower for the aquatic environment, and are located on the sides of the lower surface of the head, on the neck. The upper and lower eyes are widely separated by the cheek. Antennae short, eight- or nine-segmented, two basal segments large, 6th and 7th segments with oblong compact mace. Pronotum transverse.
Elytra either smooth, or with longitudinal rows of points, or with longitudinal grooves; naked, either with longitudinal grooves, or in short adjacent hairs, at the apex rounded, truncated, or with denticles, usually do not cover the apex of the abdomen .
Wings are normally developed [4] .
Prothorax short, transverse, with open pelvic hollows and narrow inter-pelvic processes (reduced in Orectochilinae). In contrast to other Hydradephaga, the mesothorax of vertices is much more extensive than the hind thorax , diamond-shaped. The hind coxae are very large, reaching the epipleura of the elytra. Fore tarsi long, grasping [2] ; on males, tarsi on the bottom are covered with a dense bristle of hair suckers. Middle and hind legs are swimming, short, flattened and greatly expanded, their tibia is almost triangular, the formula of the legs is 5-5-5 [4] .
Abdomen with six to seven visible sternites [4] .
Head with six eyes on each side. Mandibles are stem-shaped, with a sucking canal. Antennae four-segmented. Paws are long. The abdomen is 10-segment, with ten pairs of tracheal gills, of which two pairs are located on the ninth segment [4] .
A group of spinners on the surface of a pond (
Michigan , USA).
Both the larva and the adult beetle are predators. Adult beetles swim along the surface of water bodies (fresh) with fast zigzag movements, usually held in groups. Larvae live in the water column [4] .
In the fossil state, 11 genera and 19 species of spinners are known. The oldest finds of the family date back to the Jurassic period . All fossil twirls are imago , the only known larva found in Cretaceous Burmese amber [5] .
