Hydrometridae is a family of semiaquatic

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, known as ''marsh treaders'' or ''water measurers''. They have a characteristic elongated head and body which makes them resemble a yardstick for measuring the water surface.

Appearance

Hydrometrid bugs are of a greyish or pale brown colour, and relatively large amongst Gerromorpha at around 8 mm, although some can exceed 15 mm. Their body and

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ...

are long and slender, to the point where they resemble tiny

phasmatodea The Phasmatodea (also known as Phasmida, Phasmatoptera or Spectra) are an order of insects whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as ...

ns. The family is mostly wingless, but

winged A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expresse ...

forms do occur. The head is long as well, usually more so than the body. Their eyes are located a little behind the middle of the head and tend to bulge. Their antennae, positioned at the end of its head are four-segmented and their tarsi three-segmented .

Habitat and ecology

Marsh treaders are fairly common and have been found throughout the world. The greatest diversity, however, is found within the tropics, with only ''Hydrometra'' occurring elsewhere. The family is notable for having two genera, ''Chaetometra'' and ''Dolichocephalometra'', which are present in the Marquesas Islands where nearly all other Gerramorpha are absent . They usually occur on water surfaces at the edges of lakes, ponds, and wetlands, most often where fish are not present. They prefer aquatic vegetation or will slowly walk across calm waters, but will move quickly when disturbed . They are

predatory Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

, and will feed but also scavenge fallen animals, surface-dwelling

springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...

s being one of their favorite meals. They are also great climbers and will climb plants to find insects to eat and to lay their eggs above the water. They will use their barbed rostrum to spear their prey in the surface film . They have been generally found to have five immature stages and become adults within four to six weeks.

Systematics

The family comprises three subfamilies of seven genera, and more than 147 species are currently recognised. One subfamily is Heterocleptinae, which has tiny hairs covering its head, thorax, and base of the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

and a relatively broad and short pronotum; it comprises two genera, '' Heterocleptes'' (Villiers), of four species from

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...

, and '' Veliometra'' (Andersen), with a single species in the

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. The second subfamily is Hydrometrinae, with micro- and macro-hairs covering its entire body and the pronotum length being much shorter than the ante-ocular portion of the head. It includes the genera '' Baciliometra'' (Esaki), with four species from tropical

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

, '' Chaetometra'' (Hungerford) and '' Dolichocephalometra'' (Hungerford), two monotypic genera from the

Marquesas Islands The Marquesas Islands (; french: Îles Marquises or ' or '; Marquesan: ' ( North Marquesan) and ' ( South Marquesan), both meaning "the land of men") are a group of volcanic islands in French Polynesia, an overseas collectivity of France in th ...

, and ''

Hydrometra ''Hydrometra'' is a genus of water measurers in the family Hydrometridae Hydrometridae is a family of semiaquatic insects, known as ''marsh treaders'' or ''water measurers''. They have a characteristic elongated head and body which makes them ...

'', of at least 80 species worldwide and all North American species. The final subfamily is Limnobatodinae, which is closely related to Hydrometrinae, although it has hairs only on its head, thorax, and base of the abdomen, and pronotum longer than the ante-ocular portion of its head. It comprises a single species, ''Limnobatodes paradoxus'' (Hussey), from

Belize Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wate ...

and

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

References

{{Taxonbar, from=Q632818 Insects of Africa Hydrometroidea Heteroptera families