Evolutionary history of cockroaches

In Insect Identification

Evolutionary history of cockroaches

The cockroaches are insects that since they appeared more than 300 million years ago and during all this time have changed very little, this shows the correctness of their design and customs since they appeared.

Nearly 4000 species are known, with most of the species located between the tropics and to define their evolutionary history and phylogenetic relationships, entomologists group the Mantodea, Isoptera and Blattodea in a superorder called Dictyoptera. Current evidence suggests that termites evolved from authentic cockroaches. If this were so, then Blattodea excluding the Isoptera would not be a monophyletic group and the Isoptera would currently be a family of cockroaches.

The insects are characterized by presenting the body divided into three parts: Head, thorax and abdomen. They are flattened dorsoventrally and have an oval shape. In the head they present 2 filiform antennas that work as tactile and olfactory organs. Like all insects in the world, the Blátidos have 3 pairs of legs that come out of the thorax. It is typical of them, a protective shield (pronotum) located at the top, which covers and protects the head and chest.

At the end of the abdomen they have 2 small appendages called fences, which have a function in the capture of vibrations by air. These fences give you information about a possible predator near it.

They are nocturnal and luciferous animals, except some diurnal species. Most are omnivores although there are also xylophages and phytophages. They have defensive mechanisms, both physical and chemical, such as, excretion of substances with an unpleasant odor, presence of spines on the legs and emission of sounds. Although they are not social animals tend to gregarious. The size varies according to the species ranging from a few millimeters to more than 10 centimeters.

Regarding its nutrition, its typically chewing mouthpiece is formed by toothed plates. To the mechanical action produced by these, we must add the chemical action performed by salivary glands. Your digestive system consists of three parts: anterior tract (mouth, esophagus, crop and gizzard), middle tract (stomach and gastric blind) and posterior tract (intestine, rectum and anus).

They have a unique dorsal vessel that extends throughout the body. This tubular heart drives the hemolymph (blood). Hemolymph does not act on oxygen transport, unlike blood in higher animals. The breathing takes place through a tracheal system, which is a system of tubes that open to the outside by means of spiracles (external orifices) in the thorax and abdomen. These spiracles are easily visible to the naked eye, finding themselves in pairs in segments of the abdomen.

For all these reasons, it is amazing the most remarkable characteristic of the cockroaches, their evolutionary persistence. Just as adult individuals are very similar to young people, the passage of a few hundred million years does not seem to affect their external appearance.

More than a year ago geologists from Ohio State University characterized the largest complete fossil of a cockroach registered to date, a cockroach that lived about 300 million years ago, that is, about 55 million years before the first dinosaurs , in a then swampy area of ​​Ohio. Well, the fossil cockroach is totally similar, although larger, than the modern ones that live in the tropics.

Undoubtedly, with the cockroaches the evolution threw the rest in terms of survival capacity is concerned. Not content with adapting to how many changes our planet has suffered in the last 400 million years, the cockroach is one of the very few species that does not seem to affect the war without quarter that man has declared natural.

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