Hydrometridae
Encyclopedia
Hydrometridae is a family of semi-aquatic insect
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.
at around 8 mm, although some can exceed 15 mm. Their body and legs
are long and slender, to the point where they resemble tiny phasmatodea
ns. The family is mostly wingless, but winged
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 .
, and will feed but also scavenge
fallen animals, surface-dwelling springtail
s being one of their favourite meals. They are also great climbers and will climb plants to find insects to eat. 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.
and a relatively broad and short pronotum; it comprises two genera, Heterocleptes (Villiers), of four species from Africa
and Borneo
, and Veliometra (Andersen), with a single species in the Amazon Basin
of Brazil
. 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
, Chaetometra (Hungerford) and Dolichocephalometra (Hungerford), two monotypic genera from the Marquesas Islands
, and Hydrometra, of at least 80 species worldwide. 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
, Brazil
and Peru
.
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
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 GerromorphaGerromorpha
Gerromorpha is an infraorder of insects in the "true bug" order Hemiptera. These "typical" bugs are commonly called semiaquatic bugs or shore-inhabiting bugs...
at around 8 mm, although some can exceed 15 mm. Their body and legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
are long and slender, to the point where they resemble tiny phasmatodea
Phasmatodea
The Phasmatodea are an order of insects, whose members are variously known as stick insects , walking sticks or stick-bugs , phasmids, ghost insects and leaf insects...
ns. The family is mostly wingless, but winged
Insect wing
Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...
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
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
, 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 predatoryPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, and will feed but also scavenge
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
fallen animals, surface-dwelling springtail
Springtail
Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects...
s being one of their favourite meals. They are also great climbers and will climb plants to find insects to eat. They will use their barbed rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
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 110 species are currently recognised. One subfamily is Heterocleptinae, which has tiny hairs covering its head, thorax, and base of the abdomenAbdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
and a relatively broad and short pronotum; it comprises two genera, Heterocleptes (Villiers), of four species from Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
, and Veliometra (Andersen), with a single species in the Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. 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
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, Chaetometra (Hungerford) and Dolichocephalometra (Hungerford), two monotypic genera from the Marquesas Islands
Marquesas Islands
The Marquesas Islands enana and Te Fenua `Enata , both meaning "The Land of Men") are a group of volcanic islands in French Polynesia, an overseas collectivity of France in the southern Pacific Ocean. The Marquesas are located at 9° 00S, 139° 30W...
, and Hydrometra, of at least 80 species worldwide. 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
Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
.