Which Insects Bite Us And Why?


Out of the nearly million insect species worldwide, only a tiny proportion go out of their way to attack man; these are the highly persistent blood-suckers. Other insects that bite, stab, or sting us are just defending themselves.

Insects including mosquitoes, gnats, midges, bed bugs, and lice are all blood suckers and can cause irritation to the skin when bitten. Hornets, wasps, and bees can all sting, although this will be an act of defense.

If you want to know more about these insects, please read on.

Photo of mosquito biting skin

Mosquitoes

Blood-sucking Diptera Mosquitoes typify the outdoor blood-feeders and, like many other groups, can be highly persistent in returning again and again to their unwilling host, often in considerable numbers. If you have woken up in the morning with five or six mosquito bites in a line, as I have done many times, this is probably the culprit.

They can be found in marshy areas, as well as by ponds, lakes, and water-filled ditches, where the larvae develop.

Most mosquitoes provide warning of attack with a high-pitched whine produced by their wing beats, but other dipterous blood-suckers are far more insidious in their approach.

Some horseflies fly up and land on the skin in silence until a sharp prick betrays gives away their presence.

The small, mottled, greyish cleg is one of the most familiar and most persistent attackers, especially in thundery conditions near green vegetation.

Another problematic species is the thunder fly, conspicuous for the significant black markings on its wings.

Gnats And Midges

Many blood-sucking Diptera are extremely small, although their attention can be no less irritating. The blackflies, characterized by their large thorax, often attack in clouds near running water.

The tiny biting midges of the family Ceratopogonidae, similar to small mosquitoes but with much shorter legs, are a nuisance in damp places in summer.

By contrast, the gnats you find in winter doing their courtship dance do not suck blood.

Fleas

Fleas are close relatives of the Diptera, which have abandoned flight in favor of a different existence. They will infest various nest-building mammals and birds, exhibiting varying degrees of parasitism.

This is why you should always check your pet’s bed for fleas. Unlike adult fleas, larval fleas are not blood-suckers. Instead, they feed on skin fragments and the adult’s blood-rich excreta.

Bed And Head Pests

Bed bugs and lice present another variation on blood-suckers in that both male and female adults and the young nymphs feed on blood.

Pale brownish, the bed bug is easily recognized by its flat, almost circular abdomen, which becomes darkish red or purplish and fat after a blood meal.

Bed bugs do not spend all their time on the host’s body, feeding mainly at night and looking for cracks in the floorboards or walls during the day.

Lice are more numerous in species, the best known being the human louse which produces nits, tubular eggs attached to the roots of the hair.

How Do Insects Extract Blood?

The natural reaction of blood to any skin perforation is to clot, sealing off the wound and preventing infection.

Blood-sucking insects such as mosquitoes counter this problem by injecting an anticoagulant in their digestive saliva, which prevents clotting and allows the sucker to take an uninterrupted meal.

All blood-sucking insects have mouthparts adapted on similar lines. In bed bugs, for example, only the main and accessory jaws are used for blood-sucking, whereas in flies, the entire mouthparts may be utilized.

Disease Carriers

Insects such as mosquitoes, fleas, and lice can be disease carriers by transporting viruses, bacteria, and protozoa that cause yellow fever, typhus, plague, and malaria.

The effects of blood extraction can sometimes be quite severe, depending on the individual. Those with mild allergies or blood disorders, such as anemia, will likely experience irritation from the extractor’s saliva and anticoagulant.

Moreover, some people are more prone to the initial attack, perhaps because they overheat and sweat more readily and thus send out signals to blood-suckers.

Photo of bee

Defensive Attack

Possessing a sting for defensive purposes is almost solely confined to bees, wasps, and ants. The sting is found only in the queens and workers since the sting is a modified ovipositor.

The queen or worker may still lay eggs from the base of its ovipositor, but the remainder of this organ is given over to injecting venom.

The ovipositor of a honey bee worker has lost its egg-laying function in the course of evolution and has become modified as a defensive weapon: the sting. If a bee lands on a human and senses danger, its nervous system responds by causing specific muscles to contract. It will push out the sting, an organ consisting of two sharp lancets with barbs and a protective sheath surrounding a central sting canal.

The two lancets are lubricated by the alkaline gland and slide over one another until they sufficiently penetrate the flesh. A venom portion is pumped from the venom sac, down the sting canal, and into the victim’s tissues. Usually, the bee cannot withdraw its sting and must leave it in the flesh; in such instances, it soon dies.

In most cases, the sting is used solely against community attackers or to subdue prey. It is not often used against man unless the insect is disturbed. Even the larger hornet is of a mild disposition as far as man is concerned.

Poison Sprayer

The poisons injected by stinging insects consist of various proteins, amino acids, enzymes, and formic acid in some ants.

Wood ants are among several species that cannot inject formic acid by means of a sting. Instead, they spray it at intruders, producing a mild prickling sensation.

Some caterpillars, such as the puss moth and the lobster moth, are also capable of spraying formic acid from a special gland in the thorax, but they rarely use this as a defense against humans.

Many beetles can exude irritant substances when handled, but most of these only have a mild effect. One exception, however, is the rare blister beetle which contains a substance called cantharidin in its blood that can raise blisters on the skin.

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