Adephaga with more than 40,000 recorded species in 10 families, is a suborder of highly specialized beetles and the second largest suborder of the order Coleoptera. Members of this suborder are adephagans, a term which notably include ground beetle

Ground beetle

Ground beetles are a large, cosmopolitan family of beetles, Carabidae, with more than 40,000 species worldwide, approximately 2,000 of which are found in North America and 2,700 in Europe.-Description and ecology:...

s, tiger beetle

Tiger beetle

The tiger beetles are a large group of beetles known for their aggressive predatory habits and running speed. The fastest species of tiger beetle can run at a speed of 9 km/h , which, relative to its body length, is about 22 times the speed of former Olympic sprinter Michael Johnson, the...

s, predacious diving beetles, and whirligig beetle

Whirligig beetle

The whirligig beetles are a family of water beetles that normally live on the surface of the water. They get their common name from their habit of swimming rapidly in circles when alarmed, and are also notable for their which can see both above and below water.They are also known for their...

s. The majority of the species belong to the family of carabids, or ground beetles (Carabidae).

Anatomy

Adephagans have simple feelers with no pectination or clubs. The galea

Galea aponeurotica

The galea aponeurotica is a tough layer of dense fibrous tissue which covers the upper part of the cranium; behind, it is attached, in the interval between its union with the Occipitales, to the external occipital protuberance and highest nuchal lines of the occipital bone; in front, it forms a...

 of the first maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

 usually consists of two segments. Adult adephagans have visible notopleural

Notopleuron

The notopleuron is a region on an insect thorax. They are used in characterizing species, particularly in the Family Diptera . The notopleuron is a thoracic pleurite situated at the end of the transverse suture of Diptera.-References:* Zombori, L...

 suture. The first visible abdominal

Abdomen

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...

 sternum

Sternum (arthropod)

The sternum is the ventral portion of a segment of an arthropod thorax or abdomen.In insects, the sterna are usually single, large sclerites, and external...

 is completely separated by the hind coxa

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 ,...

e, which is one of the most easily recognizable traits of adephagans. There are 5 segments on each foot.

Wings

The transverse fold of the hindwing

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...

 is near the wing tip. The median nervure ends at this fold, where it is joined by a cross nervure.

Internal organs

Adephagans have four malpighian tubules. Unlike in other beetles, yolk chambers alternate with egg chambers in the ovarian tubes of adephagans. The coiled, tubular testes consist of a single follicle; and the ovaries

Ovary

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...

 are polytrophic.

Chemical glands

All families of adephagan have paired pygidial

Pygidium

The pygidium is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. It contains the anus and, in females, the ovipositor...

 gland

Gland

A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...

s located postero-dorsally in the abdomen

Abdomen

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...

, which are used for secreting chemicals. The glands consist of complex invaginations of the cuticle

Cuticle

A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...

 lined with epidermal

Squamous epithelium

In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...

 cells contiguous with the integument. The glands have no connection with the rectum

Rectum

The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

 and open on the eighth abdominal tergum

Tergum

A tergum is the dorsal portion of an arthropod segment other than the head. The anterior edge is called the base and posterior edge is called the apex or margin. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites...

.

Secretions pass from the secretory lobes, which are aggregations of secretory cell, through a tube to a reservoir lined with muscles. This reservoir then narrows to a tube leading to an opening valve. The secretory lobes differ structurally from a taxon to another: it may be elongate or oval, branched basally, apically or unbranched.

Delivery of glandular compounds

The secretion is realized in one of the following three manners:

• Oozing: if the gland is not muscle-lined, the discharge is limited in amount,
• Spraying: if the gland is muscle-lined, which is typically the case of carabids, the substances are ejected more or less forcefully,
• Crepitation: only associated with the Brachininae
  Brachininae
  Brachininae is a subfamily of beetles in the family Carabidae, containing the following genera:* Aptinoderus Hubenthal, 1919* Aptinus Bonelli, 1810* Brachinulus Basilewsky, 1958* Brachinus Weber, 1801* Brachynillus Reitter, 1904...
  
   carabids and several related species. See bombardier beetle
  Bombardier beetle
  Bombardier beetles are ground beetles in the tribes Brachinini, Paussini, Ozaenini, or Metriini—more than 500 species altogether—which are most notable for the defense mechanism that gives them their name: When disturbed, the beetle ejects a noxious chemical spray in a rapid burst of pulses from...
  
   for a detailed description of the mechanism.

The secretion differ in the chemical constituents, according to the taxa. Gyrinids, for instance, secrete norsesquiterpenes such as gyrinidal, isogyrinidal, gyrinidione or gyrinidone. Dytiscids

Dytiscidae

Dytiscidae – based on the Greek dytikos , "able to dive" – are the predaceous diving beetles, a family of water beetles. They are about 25 mm long on average, though there is much variation between species. Dytiscus latissimus, the largest, can grow up to 45 mm long...

 discharge aromatic aldehydes, ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s and acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, especially benzoic acid

Benzoic acid

Benzoic acid , C7H6O2 , is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. Its salts are used as a food preservative and benzoic acid is an important precursor for the synthesis...

. Carabids typically produce carboxylic acid

Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

s, particularly formic acid

Formic acid

Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...

, methacrylic acid

Methacrylic acid

Methacrylic acid, abbreviated MAA, is an organic compound. This colourless, viscous liquid is a carboxylic acid with an acrid unpleasant odor. It is soluble in warm water and miscible with most organic solvents. Methacrylic acid is produced industrially on a large scale as a precursor to its...

 and tiglic acid

Tiglic acid

Tiglic acid is a monocarboxylic unsaturated organic acid. It is found in croton oil and in several other natural products. It was also isolated from the defensive secretion of certain beetles.-Properties and uses:...

, but also aliphatic ketones, saturated esters, phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

s, aromatic aldehydes and quinone

Quinone

A quinone is a class of organic compounds that are formally "derived from aromatic compounds [such as benzene or naphthalene] by conversion of an even number of –CH= groups into –C– groups with any necessary rearrangement of double bonds," resulting in "a fully conjugated cyclic dione structure."...

s. Accessory glands or modified structures are present in some taxa: the Dytiscidae

Dytiscidae

Dytiscidae – based on the Greek dytikos , "able to dive" – are the predaceous diving beetles, a family of water beetles. They are about 25 mm long on average, though there is much variation between species. Dytiscus latissimus, the largest, can grow up to 45 mm long...

 and Hygrobiidae also possess paired prothoracic

Prothorax

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 are the pronotum , the prosternum , and the propleuron on each side. The prothorax never bears wings in extant insects, though some fossil groups possessed...

 glands secreting steroid

Steroid

A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...

s; and the Gyrinidae are unique in the extended shape of the external opening of the pygidial gland.

The function of many compounds remain unknown. Yet hypothesis have been advanced:

• Toxin
  Toxin
  A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
  
  s or feed deterrent against predators. Some compounds indirectly play this role by easing the penetration of the deterrent into the predator's integument.
• Antimicrobial
  Antimicrobial
  An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
  
   and antifungal
  Fungicide
  Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
  
   agents (especially in Hydradephaga),
• A means to increase wetability of the integument (especially in Hydradephaga),
• Alarm pheromone
  Pheromone
  A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
  
  s (especially in Gyrinidae),
• Propellant on water surfaces (especially in Gyrinidae),
• Condition plant tissues associated with oviposition
  Oviposition
  Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....
  
  .

Distribution and habitat

Habitat

Habitat (ecology)

A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...

s range from caves to rainforest

Rainforest

Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...

 canopy

Canopy (forest)

In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...

 and alpine

Alpine climate

Alpine climate is the average weather for a region above the tree line. This climate is also referred to as mountain climate or highland climate....

 habitats. The body forms of some are structurally modified for adaptation to habitats: members of the family gyrinidae live at the air-water interface, rhysodines in heartwood, paussine carabids in ant nests.

Feeding

Most species are predators. Other less typical forms of feeding include: algophagy (family Haliplidae), seed-feeding (arpaline

Harpalinae

Harpalinae is a huge subfamily of ground beetles. Among the more than 20,000 described species in this clade are the sun beetles and the violin beetles . The Harpalinae contain the most apomorphic ground beetles, displaying a wide range of forms and behaviors...

 carabids), mycophagy (rhysodine carabids), snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

-feeding (licinine

Licininae

Licininae is a subfamily of beetles in the family Carabidae, containing the following genera:* Acanthoodes Basilewsky, 1953* Actodus Alluaud, 1915* Acutosternus Lecordier & Girard, 1988* Adelopomorpha Heller, 1916...

 and cychrine carabids). Some species are ectoparasitoids of insects (brachinine

Brachininae

Brachininae is a subfamily of beetles in the family Carabidae, containing the following genera:* Aptinoderus Hubenthal, 1919* Aptinus Bonelli, 1810* Brachinulus Basilewsky, 1958* Brachinus Weber, 1801* Brachynillus Reitter, 1904...

 and lebiine

Lebiinae

Lebiinae is a subfamily of beetles in the family Carabidae, containing the following genera:* Abrodiella Bousquet, 2002* Actenonyx White, 1846* Aeolodermus Andrewes, 1929* Afrodromius Basilewsky, 1958* Afrotarus Jeannel, 1949...

 carabids) or of millipede

Millipede

Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...

s (peleciine carabids).

Reproduction and larval stage

Some species are ovoviviparous, such as pseudomorphine carabids.

The larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e are active, with well-chitin

Chitin

Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

ized cuticle, often with elongate cerci

Cercus

Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...

 and five-segmented legs, the foot-segment carrying two claws. Larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e have a fused labrum

Insect mouthparts

Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...

 and no mandibular molae.

Phylogeny

Adephagans diverged from their sister group in the late Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

, the most recent common ancestor of living adephagans probably existing in the early Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

, around 240 million years ago. Both aquatic and terrestrial representatives of the suborder appear in fossil records of the late Triassic. The Jurassic fauna consisted of trachypachids, carabids, gyrinids, and haliplid-like forms. The familial and tribal diversification of the group spans the Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

, with a few tribes radiating explosively during the Tertiary

Tertiary

The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

.

The phylogeny of adephagans is disputed. The group is usually divided into two main groups:

• The Geadephaga, comprising the two terrestrial families Carabidae and Trachypachidae (the Trachypachidae is sometimes considered a subfamily of the Carabidae), and
• The Hydradephaga, gathering all other families, which are aquatic.

This division is often criticized, as mounting evidence is pointing out that the two groups are not monophyletic.