Means of Protection in Insects
The diversity of insects’ coloration is amazing! Many of them may compete in coloration with bright multicolored flowers, while others have dull coloration, which makes them inconspicuous.
Coloration has great biological meaning. Insects, which are not protected by other means, thanks to special coloration, become hardly noticeable for predators, for birds, first of all. This type of coloration is called cryptic.
It is not only coloration that can be cryptic, but the form of the body as well. For example, mantis’ elongated body resembles a blade of grass. The cryptic coloration and form of the body of walkingsticks and caterpillars of the geometrid moth make them look like twigs.
But in some insects, the coloration as if attracts attention. Usually, such insects are well protected from predators by repulsive odor or taste, and sometimes — by venomous glands.
Such coloration is typical for many true bugs, which in case of threat release liquid with pungent unpleasant odor. Blister beetles and ladybirds release acrid substances. Some wasps with bright coloration are protected by a venomous sting. Such coloration is called warning. And birds learn not to hunt such insects.
In the world of insects, there are cases of similar appearance of two different species, when one of the species has a warning coloration and is inedible or dangerous for predators, while the other species is unprotected and mimic the former. For example, for inexperienced observer it is hard to distinguish certain hoverflies (Syrphidae) — from bees and wasps: so perfectly these hoverflies mimic their stinging relatives.
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On the surface of insects’ body there are special glands which secrete odorous substances.
Quite often this helps specimens of the same species find each other: the odor of females in mating season attracts males.
Some secretions are even edible for specimens of the same species (for example, secretions of the neck glands of male grasshoppers are licked off by females) or for other species (secretions of beetles living in anthills are licked off by ants).
In some species, glands secrete poisonous substances.
It is known that poisonous hairs of many caterpillars, for example brown-tail moths (Euproctis chrysorrhoea) can cause inflammatory processes on human skin.
Acrid protective substances are secreted by many beetles (cantharadin — blister beetles (Meloidae), pederin — some rove beetles (Staphylinidae)). Such poisons, in case of contact with skin, can cause its inflammation and necrosis.
The method of protection of the bombardier beetle is quite interesting. When threatened, it raises the back part of the abdomen, as if aiming, and then emits from the anal end of the body acrid liquid. When this liquid comes into contact with the air, it turns into vapor with loud sound, as if exploding. This is where the name bombardier comes from.