The beetles are an order of insects that has more than 350000 species which constitute the largest systematic grouping among the organisms of the planet, including plants. It is surprising to think that, according to scholars, an equally large number of species not yet known would live before our eyes, with new breeds discovered each year.
Although there may be numerous differences between one species and another, as regards specific organs and appendages, two peculiar characteristics of the external anatomy of the beetles are the exoskeleton and the elytra. The first of these is in fact a more or less rigid external structure that provides protection to the animal's body while maintaining a certain flexibility; the elytra, on the other hand, are sclerified forewings (consisting of sclerotin) which, having lost the function of flight with evolution, are a sort of shield or protection for the abdomen and the underlying membranous wings, the only ones with which animal is able to fly. There are also some families of beetles in which both the elytra and the ability to fly have been lost (family Phengodidae)
Another fundamental characteristic of beetles is the division of the body which, like all insects, includes head, thorax and abdomen.
Most beetles undergo the metamorphosis process, which involves four main phases:
- the larva,
-the pupa: in some species during this phase the beetle is enclosed in a cocoon built during the larval phase
- the adult (also called imago).
In mating beetles, the release of pheromones, substances derived from the synthesis of amino acids, fatty acids or other that allows the communication between the two companions is of considerable importance. Another particular form of mating, but limited only to fireflies, is bioluminescence, through which the couple "dialogues" before passing to mating.
Therefore courtship is very important, which can occur through particular shrill or other types of rituals, during which there can be a conflict between two specimens, so as to ensure the reproduction of the strongest.
The feeding of beetles is, as well as the species of this order, extremely varied: for the most part they are omnivorous, feeding on the remains of animals or plants in a very general way, others are more specific, and they choose to feed on arthropods or small prey such as earthworms or snails (such as carabids) or of decomposing organic matter, which constitutes the primary diet for some coprophagous beetles (which therefore feed on manure) or necrophagous sylphs (they feed on the remains of dead animals)
ECOLOGY AND RELATIONS WITH THE ENVIRONMENT
Given the large number of specimens that are part of the order of beetles the relationships that these insects have with the environment may present different differences between one family and another.
-Predation and defense: the first characteristic of many beetles is that of being prey: curious are the techniques with which each specimen defends itself from its predators, such as camouflage, which involves the use of a color mingling with the surrounding environment (one of the most widespread techniques in the animal kingdom, not only among beetles), mimicry, through which beetles like some Cerambycids emulate the physical appearance and behavior of some of their predators, so as to escape to a sad fate, or the production of unpleasant substances (ladybirds) or toxic substances (some meloids). Other beetles then use some particular body structures, such as thick and strong jaws or pointed horns (Dynastinae) to dissuade the predator to look for an easier prey;
- Parasitism: many of the beetle species are known to undertake relationships of parasitism, commensalism or predation in the strict sense with other species. In some cases there are also mutual relations, or a relationship between two or more bodies to derive a mutual benefit, as in the case of the "ambrosia" beetle, which digs tunnels in the wood of some trees bringing with them the spores of a mushroom , whose toxins allow to digest the wood itself, guaranteeing survival to the fungus and the larvae of the beetle. Many beetles are also important pests for people, finding themselves on agricultural products such as cereals, tobacco, dried fruit or cotton and many others, which can therefore cause huge damage both to human health and to crops. The opposite is the case of the beneficial action that other beetles have for humans, such as ladybirds (Coccinellidae family) which, feeding on various species of insects, guarantee a sort of "cleaning" in cultivations
- Food: some beetles are in fact considered a food source by men in 80% of the countries of the world; the larval stages are usually consumed
- Culture: in many cultures, ancient or modern, beetles have often taken on different meanings; first of all the dung beetle, which for the Egyptians was compared to the god of the rising sun (which, like the spheres the beetle composes with the faeces it feeds on, so every morning it would stick out on the horizon with the sun between its hands).
That of beetles is therefore a world in continuous discovery and evolution, which fascinates man from the dawn of its culture thanks to its unique and mysterious characteristics which scholars have always tried to discover its peculiarities.