The Haliplidae are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

water beetle A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. T ...

s that swim using an alternating motion of the legs. They are therefore clumsy in water (compared e.g. with the

Dytiscidae The Dytiscidae, from the Ancient Greek word δυτικός (''dystikos''), meaning "able to dive", are the predaceous diving beetles, a family of water beetles. They occur in virtually any freshwater habitat around the world, but a few species l ...

Hydrophilidae Hydrophilidae, also known colloquially as water scavenger beetles, is a family of beetles. Aquatic hydrophilids are notable for their long maxillary palps, which are longer than their antennae. Several of the former subfamilies of Hydrophilidae ...

), and prefer to get around by crawling. The family consists of about 200

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

in five

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 ...

, distributed wherever there is

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

; it is the only extant member of

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Haliploidea. They are also known as crawling water beetles or haliplids.

Description

The adults of these beetles are generally oval in shape, with a very convex upperside, and are generally long. They are generally yellowish to light brown in color, frequently with light and dark patterns dotted with 10 or more rows of punctures on the

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

. The family's most distinctive characteristic is the large coxal plates of the hindlegs, which are immobile (though not fused in the centerline) and extend back along the underside to cover most of the

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

base and the hindleg trochanters and femora. They are used as air storage supplementing the air carried under the elytra. The

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

s are markedly protruding from a smallish head, which bears antennae with 11 segments set upon an antennophore with a conspicuously short base ( scapus). The extension of the

prosternum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

is broad, with a truncated tip, ending adjacent to the metasternal process. The metasternum has a complete transverse ridge. The slender legs have long swimming hairs on tibiae and tarsi, but are not flattened into " flippers". The foreleg tibiae lack the apparatus for antenna cleaning present in many other beetles. Unlike in other

Adephaga The Adephaga (from Greek ἀδηφάγος, ''adephagos'', "gluttonous") are a suborder of beetles, and with more than 40,000 recorded species in 10 families, the second-largest of the four beetle suborders. Members of this suborder are collecti ...

, the hindwings are not folded under the elytra, but rolled together apically. Haliplus fulvus larva

Haliplidae

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e have a long and slender body with a tough

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

. They can be recognized by their specialized mouthparts, carried on a small head. The

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

e and labium are

adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...

to manipulating the

alga Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

e the larvae feed on, while the

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

s contain a channel through which fluids are sucked out of the food. The larval legs are short and carry a single claw each, but the forelegs have various adaptations for climbing among

water plant Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...

Respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

is via

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

which are either long and filamentous, or (as in ''

Peltodytes ''Peltodytes'' is a genus of water beetle which is native to the Nearctic, Europe, the Near East, and North Africa. ''Peltodytes'' can generally be differentiated from the similar ''Haliplus'' by the presence of a pair of spots on the posterior m ...

'') short microtracheal extensions; they are carried on the

tergite A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the Anatomical terms of location#Dorsal and ventral, dorsal ('upper') portion of an arthropod segment other than the head. The Anatomical terms of location#Anterior ...

s of each thoracic segment and all but the ninth or tenth abdominal segment, whichever is terminal. The latter may be absent, but in the larvae of some Haliplidae it is tapering and ends in two prongs (which are not urogomphi though). The last (third)

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

has functional spiracles on the

mesothorax The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum (dorsal), the mesosternum ( ventral), and the mesopleuron (lateral) ...

and the first to seventh abdominal segments.

Ecology

Haliplids live in the aquatic vegetation around the edges of small ponds, lakes, and quiet streams. Adults are

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

, eating insect eggs, small

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

hydrozoa Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomy (biology), taxonomic class (biology), class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline wat ...

n polyps, and algae, while the

e eat only

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

. The species of ''

'' deposit

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

on the surface of aquatic plants, while '' Haliplus'' chews out a cavity in the plants for their eggs. There are three

s, and

pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

tion takes place on land in a chamber constructed by the larva. Crawling water beetles are not extensively studied because their interaction with humans is minimal. Hungerford's crawling water beetle (''Brychius hungerfordi'') is an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

found only in

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

and

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

Systematics

The classification of haliplids as a separate group of

is unquestioned, and most

entomologist Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...

s believe they developed from terrestrial beetles separately from other types of water beetles. For many decades, the family was in need of revision, the last general catalog being published by A. Zimmermann in 1920. B. J. van Vondel produced an updated catalogue of the known Haliplidae taxa. Like predaceous diving beetles (

), the crawling water beetles form an early offshoot of the Adephaga. They still have grooved

e and their tentoriolacinial muscle does not attach to the mesal stipial base. Their larvae, like those of predaceous diving beetles, do not possess eggshell-bursters on the head. It is not yet resolved whether Haliplidae and Dytiscidae are closest relatives, or whether they originated independently from the basal Adephaga.

Genera

The family is not very diverse, with only five

accepted.Haliplidae Species List
at Joel Hallan's Biology Catalog. Texas A&M University. Retrieved on 10 May 2012. Of these, ''Peltodytes'' is probably the most ancestral, though it has a number of

autapomorph In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

ies. The others have more

synapomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

ies in common; ''Haliplus'' is the more diverse and appears to include some minor lineages formerly considered independent genera.

References

External links

Haliplidae
Tree of Life {{Authority control Beetle families Taxa named by Charles Nicholas Aubé