Autohaemorrhaging, or reflex bleeding, is the action of animals deliberately ejecting

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

from their bodies. Autohaemorrhaging has been observed as occurring in two variations. In the first form, blood is squirted toward a predator. The blood of these animals usually contains toxic compounds, making the behaviour an effective chemical

defense mechanism In psychoanalytic theory, defence mechanisms are unconscious psychological processes that protect the self from anxiety-producing thoughts and feelings related to internal conflicts and external stressors. According to this theory, healthy ...

. In the second form, blood is not squirted, but is slowly emitted from the animal's body. This form appears to serve a deterrent effect, and is used by animals whose blood does not seem to be toxic. Most animals that autohaemorrhage are insects, but some reptiles also display this behaviour. Some organisms have shown an ability to tailor their autohaemorrhaging response. Armoured crickets will projectile autohaemorrhage over longer distances when attacked from the side, compared to being attacked from an overhead predator.

Insects

Several orders of insects have been observed to utilize this defence mechanism. *

Beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s **

Meloidae Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their ...

(blister beetles) – their haemolymph contains

cantharidin Cantharidin is an odorless, colorless fatty substance of the terpenoid class, which is secreted by many species of blister beetles. Its main current use in pharmacology is treating molluscum contagiosum and warts topically. It is a burn agent ...

that they sequester from plants on which they feed. One of the known species is ''

Meloe americanus ''Meloe americanus'' is a type of blister beetle (Meloidae) found in North America. It is most relevant to the fields of agriculture and veterinary medicine. Adult beetles feed on different types of plants, which cause crop damage. They also rele ...

''. **

Tenebrionidae Darkling beetle is the common name for members of the beetle family Tenebrionidae, comprising over 20,000 species in a cosmopolitan distribution. Taxonomy ''Tenebrio'' is the Latin generic name that Carl Linnaeus assigned to some flour beetles ...

(darkling beetles) - larvae of ''

Asbolus verrucosus ''Asbolus verrucosus'' (LeConte, 1852), also known as the desert ironclad beetle or blue death feigning beetle, is a species of darkling beetle native to southwestern United States (southern California to Utah and New Mexico) and northwestern Mex ...

'' have been observed to autohaemorrhage while they feign death. **

Chrysomelidae The beetle family Chrysomelidae, commonly known as leaf beetles, includes over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making it one of the largest and most commonly encountered of all beetle families. Numerous s ...

, incl. ''

Timarcha ''Timarcha'' is a genus of leaf beetles in the family Chrysomelidae, with more than 100 described species in three subgenera. The most widely known species is ''T. tenebricosa'', the bloody-nosed beetle. All species are black, wingless organisms ...

'' species - their haemolymph contains

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic hydrocarbon, aromatic organic compound with formula . Several isomers exist but these terms usually refer to 9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein th ...

s. **

Coccinellidae Coccinellidae () is a widespread family (biology), family of small beetles. They are commonly known as ladybugs in North America and ladybirds in the United Kingdom; "lady" refers to Mary, mother of Jesus, mother Mary. Entomologists use the ...

(ladybird, ladybug or lady beetles) – An alkaloid toxin in the haemolymph is exuded through the joints of the

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 ...

, triggered by mechanical stimulation (such as predator attack). *

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 ...

Cercopidae Cercopidae are the largest family of Cercopoidea, a xylem-feeding insect group, commonly called froghoppers. They belong to the hemipteran suborder Auchenorrhyncha. A 2023 phylogenetic study of the family suggested the elevation of the New Worl ...

– including

spittlebugs Cercopidae are the largest family of Cercopoidea, a xylem-feeding insect group, commonly called froghoppers. They belong to the hemipteran suborder Auchenorrhyncha. A 2023 phylogenetic study of the family suggested the elevation of the New Worl ...

Prosapia bicincta ''Prosapia bicincta'', the two-lined spittlebug, is a species of insect in the family Ischnorhinidae (formerly Cercopidae). Adults are black with two red or orange lines crossing the wings. It reaches a length of 8–10 mm. It is widespread ...

'' and ''Prosapia ignipectus'' *

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

Tiger moth The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary trainer aircraft. ...

adults, such as ''

Arctia caja The garden tiger moth or great tiger moth (''Arctia caja'') is a moth of the family Erebidae. ''Arctia caja'' is a northern species found in the United States, US, Canada, and Europe. The moth prefers cold climates with temperate seasonality, as ...

'', which mixes haemolymph with glandular products (neurotoxic choline esters). *

Orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – gras ...

** Bushhoppers, such as ''

Dictyophorus spumans ''Dictyophorus spumans'', the koppie foam grasshopper, , or African foam grasshopper, is a species of grasshopper in the family Pyrgomorphidae indigenous to southern Africa. The name "foaming grasshopper" derives from the insect's ability to prod ...

'', ''

Phymateus viridipes ''Phymateus viridipes'', also known as the green milkweed locust or African bush grasshopper, is an African locust in the family Pyrgomorphidae (gaudy grasshoppers). Body characteristics It is about long at maturity and capable of long migrat ...

'' and ''

Phymateus leprosus ''Phymateus'' is a genus of fairly large grasshoppers of the family Pyrgomorphidae, native to shrubland, semi-deserts, savanna, woodland, gardens and cultivated areas in Sub-Saharan Africa, with ten species in the African mainland and two species ...

'' – their haemolymph contains cardiac

glycosides In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

, sequestered from

milkweed ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to huma ...

on which they feed. **

Katydid Insects in the family Tettigoniidae are commonly called katydids (especially in North America) or bush crickets. They have previously been known as "long-horned grasshoppers". More than 8,000 species are known. Part of the suborder Ensifera, the ...

s, including '' Eugaster'' species and ''

Acanthoplus discoidalis ''Acanthoplus discoidalis'' is a species in the Hetrodinae, a subfamily of the katydid family (Tettigoniidae). Like its closest relatives, ''Acanthoplus discoidalis'' variously bears common names such as armoured katydid, armoured ground crick ...

'' *

Plecoptera Plecoptera is an order (biology), order of insects commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to b ...

Stonefly Plecoptera is an order of insects commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the most ...

larvae

Reptiles

Tropidophis_curtus_barbouri_autohaemorrhaging

Lizards

* Horned lizards (

Phrynosomatidae The Phrynosomatidae are a diverse family of lizards, sometimes classified as a subfamily (Phrynosomatinae), found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny ...

). At least six species of horned lizards are able to squirt an aimed stream of blood from the corners of their eyes, up to 5 feet (1.5 m).

Snakes

* West Indian wood snake (''

Tropidophis ''Tropidophis'', common name Caribbean dwarf boas, wood snakes or West Indian wood snakes,Hampton Wildman Parker, Parker HW, species:Alice Georgie Cruickshank Grandison, Grandison AGC (1977). ''Snakes — a Natural History''. Second Edition. Lond ...

''). Thirteen species have been found to expel blood from the mouth and nostrils while also fully flooding both eyes with blood. * European grass snake (''

Natrix natrix The grass snake (''Natrix natrix''), sometimes called the ringed snake or water snake, is a Eurasian semi-aquatic non-venomous colubrid snake. It is often found near water and feeds almost exclusively on amphibians. Subspecies Many subspecies ...

''), which secretes blood from the lining of the mouth while playing dead. * Long-nosed snake (''

Rhinocheilus lecontei ''Rhinocheilus'' is a genus of snakes, commonly called the long-nosed snakes, in the family Colubridae. The genus is native to the western United States and Mexico. Species and subspecies The genus ''Rhinocheilus'' contains the following specie ...

''), which exudes blood from the cloaca. * Eastern hognose snake ( ''Heterodon'' ''platirhinos''), which emits blood from the cloacal region. * Plain-bellied water snake (''

Nerodia erythrogaster ''Nerodia erythrogaster'', also known as the plain-bellied water snake or plainbelly water snake, is a common species of semi-aquatic, non-venomous colubrid snake endemic to the United States. Description The plain-bellied water snake is a larg ...

''), which releases blood from the mouth. * Western hognose snake (''

Heterodon nasicus The western hognose snake (''Heterodon nasicus'') is a species of snake in the family Colubridae. The species is endemic to North America. There are three subspecies that are recognized as being valid, including the nominotypical subspecies. Et ...

''), which releases blood from the mouth.

Consequences of reflexive bleeding

In some cases, the loss of blood can be substantial. Beetles may lose up to 13% of their net body weight as a consequence of expelling haemolymph. Autohaemorrhaging may result in dehydration. The ejection of blood puts organisms at risk of cannibalism from other members of their species.

References

External links

*{{commonscat-inline, Autohaemorrhaging, Autohaemorrhaging Antipredator adaptations Blood Insect physiology