Marsh treader
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Marsh treaders (family Hydrometridae), or water measurers, are semiaquatic insects. They have a characteristic elongated head and body which make them appear as yardstick for measuring the water surface.
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[edit] Taxonomy
The family comprises three subfamilies of seven genera, and more than 110 species are currently recognized. One subfamily is Heterocleptinale, which has tiny hais covering its head, thorax, and base of the abdoman and a relatively broad and short pronotum, comprising two genera, Hetercleptes (Villiers), of fours species from Africa and Borneo, and Veliometra (Andersen), of one species in the Amazon Basin in Brazil. The second is Hydrometrinae, with micro- and macro-hairs covering its entire body and the pronotum length being much shorter than the anteocular portion of the head. It includes the genera of Baciliometra (Esaki), of four species from tropical South America, Chaetometra (Hungerford) and Dolichocephalometra (Hungerford), both of one species from the Marquesas Islands, and Hydrometra, of at least 80 species worldwide. The final subfamily is Limnobatodinae, which is closely related to Hydrometrinae, though it has hairs only on its head, thorax, and base of the abdomen, and pronotum longer than the anteocular portion of its head. It comprises only one species, Limnobatodes paradoxus (Hussey), from Belize, Brazil, and Peru.[1]
[edit] Appearance
Marsh treaders are of a grayish or pale brown color, and relatively large amongst Gerromorpha at around 8 mm, though sometimes but rarely exceed 15 mm. Their body and legs are long and slender, to the point where they resemble tiny walking sticks. 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,[2] are four-segmented and their tarsi three-segmented.[3]
[edit] Habitat and ecology
Marsh treaders are fairly common and have been found throughout the world. However the most diversity is within the tropics, with only Hydrometra occurring elsewhere. The family is notable for having two genera, Chaetometra and Dolichocephalometra, being present in the Marquesas Islands where nearly all other Gerramorpha are absent.[1] They usually occur on water surfaces at the edge lakes, ponds, and wetlands, most often where fish are not present. They prefer aquatic vegetation or will slowly walk across calm waters, though will move quickly when disturbed.[3] They are predacious, and will feed but also scavange fallen animals and arthropods, surface-dwelling springtails being one of their favorite 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.[4] They have been generally found to have five immature stages and become adults within four to six weeks.
[edit] Notes
- ^ a b Schuh, Randall T; Slater, James A (1995). True Bugs of the World (Hemiptera: Heteroptera). Cornell University Press. p. 95-6. ISBN 0801420660.
- ^ Tsyrlin, Edward; Gooderham, John (2002). The Waterbug Book: A Guide to the Freshwater Macroinvertebrates of Temperate Australia. CSIRO Publishing. p. 153. ISBN 0643066683.
- ^ a b Borror, Donald Joyce, et al (1998). A Field Guide to Insects: America north of Mexico. Houghton Mifflin Field Guides. p. 125-6. ISBN 0395911702.
- ^ Thorp, James H; Covich, Alan P (1991). Ecology and Classification of North American Freshwater Invertebrates. Elsevier. p. 617. ISBN 0126906459.
