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Sting (biology)

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Sting (biology)

For other uses, see Stinger (disambiguation).

A stinger or sting[1] is a sharp organ found in various animals (typically arthropods) that delivers venom (usually piercing the skin of another animal). A true sting differs from other piercing structures in that it pierces by its own action and injects venom, as opposed to teeth, which pierce by the force of opposing jaws. Stinging hairs which actively inject venom on plants such as stinging nettles are also known as stings, but not stingers.[2]

Insect bite and sting is a break in the skin or puncture caused by an insect and complicated by introduction into the skin of the insect's saliva, venom, or excretory products. Specific components of these substances are believed to give rise to an allergic reaction, which in turn produces skin lesions that may vary from a small itching wheal, or slightly elevated area of the skin; to large areas of inflamed skin covered by vesicles and crusted lesions. This article encompasses similar wounds inflicted by other small invertebrates, particularly arachnids (spiders, scorpions, ticks, mites, and their allies).

Flying insects, such as flies, gnats, and mosquitoes, attack exposed body parts, each bite resulting in a single itchy wheal that generally subsides within hours. Crawling insects may reach any part of the body, including the covered areas, and are more likely to remain there, generating skin diseases characteristic of each insect. Scabies, or sarcoptic itch, designates the skin inflammation brought about by the itch mite, Sarcoptes scabiei. The female mite burrows beneath the superficial layer of the skin to lay its eggs in a tunnel that can be seen as a dark wavy line. This initial lesion becomes intensely itchy after a few days to about a month, and the scratching leads to secondary skin lesions consisting of papules (solid elevations), pustules, and crusted skin areas. The itchiness is believed to be caused by the accumulation of fecal deposits by the mite in the burrow region. Scabies is most commonly noted on the webs between the fingers, other frequent locations being the natural folds of the skin and pressure areas.

Pediculosis is the skin disorder caused by various species of bloodsucking lice that infect the scalp, groin, and body. The lice live on or close to the skin and attach their eggs to the hair or clothing of the host, on which they periodically feed. Their bite results in a small red spot that is extremely itchy and may become infected after repeated scratching. Chiggers, the larvae of certain mites, also live on humans and feed on blood. Their bite produces a wheal on the skin that is intensely itchy, the itchiness being caused by the digestive juices of the chiggers. Other bloodsucking insects that feed on humans are fleas, bedbugs, and ticks, which do not live on humans as primary hosts but in the ground, bedding, walls, and furniture; the more commonly seen lesions are those of the bedbug, which produces a burning wheal with a central punctured dot, and those of the flea, which produces a cluster of wheals and papules, resulting from the flea's habit of sampling several adjacent spots while feeding on the skin.

Stinging insects produce a painful swelling of the skin, the severity of the lesion varying according to the location of the sting and the identity of the insect. Many species of bees and wasps have two poison glands, one gland secreting a toxin in which formic acid is one recognized constituent, and the other secreting an alkaline neurotoxin; acting independently, each toxin is rather mild, but when they are injected together through the stinger, the combination has strong irritating properties. In a small number of cases the second occasion of a bee or wasp sting causes a severe allergic reaction known as anaphylaxis.

Hornets, some ants, centipedes, scorpions, and spiders also sting. Some insects leave their stinger in the wound. Multiple stings may give rise to severe systemic symptoms and in rare instances may even lead to death; the bites of some spiders are known to be lethal, particularly to young children.

Arthropods

The main type of construction of stings is a sharp organ of offense or defense, especially when connected with a venom gland, and adapted to inflict a wound by piercing; as the caudal sting of a scorpion. The wasp has a very painful sting, and will sting if it feels threatened.

Stings are usually located at the rear of the animal. Animals with stings include bees, wasps (including hornets), scorpions[3] and some groups of ants.

Unlike most other stings, honey bee workers' stings (a modified ovipositor as in other stinging Hymenoptera) are strongly barbed and lodge in the flesh of mammals upon use, tearing free from the honey bee's body, leading to the bee's death within minutes.[3] The sting has its own ganglion and it continues to saw into the target's flesh and release venom for several minutes. This trait is of obvious disadvantage to the individual but protects the colony, comprising many sterile workers who are all sisters, from attacks by large animals; the shared genes of the colony are more likely to be passed on if it is defended vigorously. The barbs ensure that a honey bee's attack is only suicidal if the attacker is a relatively large animal; bees can sting other insects repeatedly and without dying. The sting of nearly all other bees and other stinged organisms is not barbed and can be used to sting mammals repeatedly; the barbs on the stingers of yellowjacket wasps and the Mexican honey wasp are so small that they do not cause the sting apparatus to pull free.

Other animals

Organs that perform similar functions in non-arthropods are often referred to as "stings", although they are all technically considered to be something else (e.g., a venomous barb). These include the modified dermal denticle of the stingray, the venomous spurs on the hind legs of the male platypus, and the cnidocyte tentacles of the jellyfish.

The term sting was historically often used for the fang (a modified tooth) of a snake,[4] although this usage is uncommon today; snakes are said, correctly, to bite, not sting.

Plants

In plants, the term "sting" is normally used as a verb, but occasionally used as a noun refer to urticating hairs; sharp-pointed hollow hairs seated on a gland which secretes an acrid fluid, as in species of Urtica (nettles). The points of these hairs are brittle and break off easily, leaving a sharp point like a hypodermic needle, through which the fluid is injected.[5]

See also

References

External links

Arthropods portal
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