Insects, ancient lords of the air
If asked to answer the question: "What is the most widespread group of winged animals on Earth?", Most likely, in most cases, the answer would be "The Birds".
The equation: wings = bird is true, but if we consider, for example, the number of species of Birds and Insects (yes, "Insects" was the right answer!) classified so far, the figures speak for themselves: about 10,000 are the species with feathers and beak against more than a million species of Insects that flies here and there in every corner of our planet!
However, exceptions in the natural world are the rule, therefore not all insects possess wings, either because they never had them (Apterygotes) or because they subsequently lost them by specialization as a result of evolution (atteri); also there are species that fly among which not all individuals are the same, and some of these are wingless.
In addition, the wings can also be very different, in the various species, and also have different functions.
Complicated? But no! Let's see, on the fly, some examples!
A flight that comes from afar
We begin to say that the Insects are most probably among the most ancient organisms that have conquered the emerged lands; insect fossils have been found that belong to the fourth period of the Paleozoic era, the Devonian, which dates back to between 416 and 359 million years ago. The famous Meganeura monyi , a giant dragonfly with a wingspan of 75 cm, dates back to the next Carboniferous!
Insects are found in every environment, and are believed to represent 90% of life forms currently present on our planet! Surely there are many species not yet discovered. Particularly in ecosystems such as the Amazon rainforest that we are devastating, so very little will remain to be discovered and it will disappear even before we have cataloged it. Beyond this demoralizing but necessary parenthesis, it is therefore easy to understand how the great diversification of these animals may have produced an enormous variety of structures and functions to adapt to different environmental conditions: wings may well represent this concept.
Wings not only for flying
The wings are flattened plates, in which, within special ducts, called ribs or veins, the hemolymph flows and nerves and trachea pass through; they are at most 4 and, as we said, not all insects have them; they are therefore divided, precisely on the basis of this characteristic, in Pterygoti (from the Greek pterygōtós, which means “winged”) and in Apterigoti, in fact, without wings. The latter are represented by a single order, the Tisanuri, authentic living fossils; some of them are known as "silverfish", and belong to the suborder Lepismida, such as the species Lepisma saccharina.
The wings, for taxonomic investigations, are of great importance, since they are the structure that allows the identification and classification of the different types of insects: orders and families have wings with numerous characteristics of their own; including the shape, structure, color, but also the position in the animal's body.
Some Odonata Anisoptera, such as dragonflies, or certain Zygoptera, such as damsels, when at rest, instead of folding their wings, spread them horizontally; the representatives of Trichoptera, freshwater insects, and Plecoptera, on the other hand, keep them inclined.
In the Beetles, the front wings are called elytra, they are resistant and sclerified (i.e. they have undergone a process that has allowed them to accumulate chitin, a polymer that gives hardness) and have a protective function, both of the body and of the real wings used for flight, which keep folded up through complicated joints, under the elytra.
Some Orthoptera, such as locusts, grasshoppers and crickets, have two pairs of wings; the anterior ones, called tegmine, have a protective function, but also of a stridulating apparatus; they are slightly sclerified, while the posterior ones are membranous and wide, sometimes brightly colored. A similar structure is noted between the Hemiptera, which are divided into Heteroptera (the classic plant bugs) with the first pair of semi-membranous wings, and Homoptera, with all four membranous wings (an example known to all: cicadas), in some cases transparent, in others opaque or with splendid colors.
Different types of wings
Butterflies have four wings, two front and two rear, often magnificently colored and with extraordinary designs, even in some nocturnal butterflies, contrary to popular belief, covered with flakes (butterflies are Lepidoptera, which literally means "wings with scales") arranged like the tiles covering a house (imbricate); in most of the species, the scales contain colored pigments, which give the colors and multiple designs to the liveries that characterize these delicate animals.
In other cases, the coloring is due to particular physical phenomena of refraction, that is, not to pigments, but to the structure of the wing. The classic example is the butterflies of the Morphidae family, often with metallic blue colors.
Termites belong to the Isoptera group and are social insects, as their society is divided into castes. They have amphipecyl polymorphism: there are the royals, that is, the fertile caste, composed of male and female fertilized individuals, initially winged, and the sterile one, composed of workers and soldiers, without wings.
A similar fate is that of ants, social Hymenoptera, where individuals with wings are only the reproducers, that is, young males and young queens who participate in the nuptial flight during mating; even in these animals there are castes, and here too the worker ants and soldiers are wingless.
