Water Scorpion
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Nepidae is a family of exclusively aquatic
Heteroptera The Heteroptera are a group of about 40,000 species of insects in the order Hemiptera. They are sometimes called "true bugs", though that name more commonly refers to the Hemiptera as a whole. "Typical bugs" might be used as a more unequivocal al ...
n
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
s in the order
Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from ...
.Nepidae, Tree of life project
/ref> They are commonly called water scorpions for their superficial resemblance to
scorpion Scorpions are predatory arachnids of the Order (biology), order Scorpiones. They have eight legs and are easily recognized by a pair of Chela (organ), grasping pincers and a narrow, segmented tail, often carried in a characteristic forward cur ...
s, due to their raptorial forelegs and the presence of a long slender process at the posterior end of the abdomen, resembling a tail. There are 14 genera in the family, in two subfamilies, Nepinae and Ranatrinae. Members of the genus '' Ranatra'', the most widespread and species-rich genus, are sometimes called needle bugs or water stick insects as they are slenderer than ''
Nepa The National Environmental Policy Act (NEPA) is a United States environmental law designed to promote the enhancement of the environment. It created new laws requiring List of federal agencies in the United States, U.S. federal government agenc ...
''. While water scorpions do not sting with their tail (it is used for breathing), they do have a painful bite (strictly speaking a sting by their pointed
proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...
), but this is much less harmful to humans than a true scorpion's sting.


Range and habitat

Nepidae are found on all continents except Antarctica. They mostly inhabit stagnant or slow-moving freshwater habitats like ponds, marshes, canals and streams. Exceptionally they have also been recorded from
hypersaline lake A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing those of ocean water (3.5%, i.e. ). Specific microbial species can thrive i ...
s and
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
lagoons, the Australian genus ''Goondnomdanepa'' is restricted to flowing waters, and ''Nepa anophthalma'' is adapted to life in caves in
Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
.


Appearance and ecology

Nepidae are brown insects, but some species have a bright red abdomen that can be seen when the wings are open. Their body is broad and flat (subfamily Nepinae) or long and thin (subfamily Ranatrinae). They are rather poor swimmers and typically crawl about on aquatic vegetation. They can fly, but this is infrequently seen. In most species the body is between long, although the largest such as the East Asian ''Ranatra chinensis'' and South American ''R. magna'' can approach . Respiration in the adult is achieved by means of the caudal process, which consists of a pair of half-tubes capable of being locked together to form a
siphon A siphon (; also spelled syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, abo ...
. Air is conducted through it to the
trachea The trachea (: tracheae or tracheas), also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals' lungs. The trachea extends from ...
e at the
apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...
of the abdomen when the tip of the tube is thrust above the surface of the water (similar to a snorkel). In some species the siphon is longer than the body, but in others it is shorter, in a few even less than one-tenth of the body length. In immature forms the siphon is often underdeveloped and respiration takes place through six pairs of abdominal spiracles. To keep their orientation in the water they have three pairs of “static sense organs”, small oval structures closely associated with the fourth, fifth, and sixth abdominal spiracles. Their frontal legs are modified into raptorial appendages that are used to grab their prey. They feed primarily on aquatic invertebrates such as other insects, but occasionally take small fish or tadpoles. The eggs, which are laid above the waterline in mud, decomposing vegetation, the stems of plants or rotting wood, are supplied with air by filamentous processes which vary in number among the genera.


Subfamilies and genera

Nepidae has around 250 species in 14
genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
divided into two
subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zool ...
, Nepinae and Ranatrinae. Among these the most diverse are the widespread ''Ranatra'' (about 100 species) and ''Laccotrephes'' (about 60), but the family also includes species-poor genera, like the
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
n ''Borborophilus'', ''Nepella'', ''Nepitella'' and ''Paranepa'' (each with one species), Indian ''Montonepa'' (one species), Philippine ''Borborophyes'' (one species), and Australian ''Austronepa'' (one species) and ''Goondnomdanepa'' (three species). '' Araripenepa'' from the Early Cretaceous (
Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
)
Crato Formation The Crato Formation is a geologic formation (stratigraphy), formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätten, Lagerstätte (undisturbed fossil accumulation) for palaeontology, pa ...
of Brazil is the oldest known member of the family, and is the sister group to remaining genera.


Ranatrinae

Authority: Douglas & Scott, 1865 (sometimes called "water stick insects") Genera in this subfamily include: ''Austronepa'' and ''Goondnomdanepa'' are restricted to Australia. '' Cercotmetus'' is from Asia to northern Australia and resembles '' Ranatra'' (Worldwide distribution), although the former has a distinctly shorter siphon. #'' Austronepa'' Menke & Stange, 1964 #'' Cercotmetus'' Amyot & Serville, 1843 #'' Goondnomdanepa'' Lansbury, 1974 #'' Ranatra'' Fabricius, 1790


Nepinae

Authority: Latreille, 1802 (sometimes called "water scorpions") *'' Borborophilus'' *'' Borborophyes'' *'' Curicta'' *'' Laccotrephes'' *'' Montonepa'' *''
Nepa The National Environmental Policy Act (NEPA) is a United States environmental law designed to promote the enhancement of the environment. It created new laws requiring List of federal agencies in the United States, U.S. federal government agenc ...
'' *'' Nepella'' *'' Nepitella'' ( syn. ''Nepita'') *'' Paranepa'' *'' Telmatotrephes''


See also

*
Eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...
: unrelated, extinct arthropods that are commonly called sea scorpions


References


External links

* *
Water Scorpions


{{Hemiptera, 3 Heteroptera families