Velvet water bug

Velvet water bugs are members of the family Hebridae. They are semiaquatic insects that live among moss or ponds with an abundance of vegetation, in which they prey on small arthropods. Velvet water bugs are the smallest of the Gerromorpha, and have an appearance of tiny veliids. Hebrids sometimes move across water surfaces, but walk or run rather than skate or scull on the surface.

Appearance

Hebrids are small, ranging from lengths of 1.3 to 3.7 mm. They have a characteristic layer of short, dense hairs that cover their entire body, except on their abdomen and appendages, from which they derive the common name "velvet water bug". They have tarsi in two segments, with their hing legs shorter than their body. Unlike Veliidae and Mesoveliidae, they are known only as winged forms.^[1] These wings however may be anywhere from well-developed, to short or lacking. The wing's membrane, when it is present at all, lacks any distinct veins that are common of shore bugs Saldidae. They are typically darkly-colored. The beak of Hebrids is long and reach to their middle pair of legs, and sits in a ventral groove on their head.^[2] They also have apical claws, lacking the preapical claws of Veliidae. Their pronotum is broad, usually more so than the rest of the body.^[3]

Habitat

The Velvet Water Bug lives on floating vegetated portions of ponds, or similar regions which are permanently damp, which could be inside mats of moss or in interstices, but also sloping stream banks which may have sparse vegetation. Certain species may be adapted to a particular habitat. Members of the genera Timasius and Hebrometra for instance, live on waterwashed rocks near in stream or waterfalls. A few species are able to tolerate saline, brackish, or marine conditions. One species, Hebrus ruficeps, can tolerate being frozen overwinter in ice among Sphagnum. The original common habitat of this family however was probably humid terrestrial or marginally aquatic.^[4]

Hebrids lay their eggs anywhere on some sort of substrate, like on a moss, but will attach them lengthwise with a gel-like substance.They are found worldwide, with their greatest diversity in Asian tropical regions.^[5]

Systematics

Hebridae is the only family within the superfamily Hebroidea.^[6] There are around 160 species placed in seven genera. Hebrids are divided between two recognized subfamilies. The first is Hebrinae, which have eyes located near the base of the head, and antennae that are clearly longer than the head, and the parameres is generally symmetrical. It includes the genera of Hebrometra (Cobben), a genus of four species from Ethiopia, Hebrus (Curtis), the family's largest genus consisting of 110 species, Lipogomphus (Berg), four species from the Americas, Merragata (Buchanan-White), of several species, Neotimasius (Andersen), of one southern Indian species, and Timasius (Distant), a genus of 15 species that ranges from Sri Lanka to Taiwan. The second subfamily is Hyrcaninae, which have eyes clearly removed from the pronontum's anterior margin. The length of the antennae is less or equal to that of the head. Also the ventral arolium is distinctly longer than the dorsal arolium, and the parameres is symmetrical. This subfamily has only one included genus, Hyrcanus (Distant), of four Asian species.^[5]

Notes