Pterothorax ( pterothorax ) is a concept that combines the middle and posterior segments of the chest of insects . This concept is functional, not anatomical, so some structural details that would radically distinguish it from the prothorax do not exist. However, it has a number of important structural features.
The insect chest consists of three annular parts, with a pair of legs attached to each of them in the lower part. The second and third segments (mesothorax and metothorax) also bear two wings each. For this reason, the middle and posterior thoracic segments are conventionally combined into a common section, the pterothorax, which in semantic translation from Greek means “the part of the chest that is responsible for the flight” [1] .
Isolation of pterothorax into a separate area is associated with the insects' ability to fly — a powerful evolutionary factor that elevated them to a higher stage of development, allowed them to spread over a large area and ensured the continued prosperity of many of their biological species [2]
Like the prothorax, the pterothorax segments consist of two half rings (upper - tergite , lower - sternite ), interconnected by lateral plates ( playrites ). Between the mesothorax and the labia there is a strong or mobile transverse seam. In most insects, it is noticeable quite clearly, as it is presented in the form of a deep groove [3] .
Evolutionists believe that the deep suture between the segments of the breast is due to the fact that during the evolution, with the advent of wings, the insects needed more powerful muscles to move. As a result of this, the middle and back sections of flying species increased in volume, and the place of their connection remained unchanged.
The classic shape and size of pterothorax are dragonflies , which are almost all the time in flight. These insects are generally unable to walk - tired out, they sit down for a while and then take off again. In all flying insects, pterothorax is a durable, chitinized body, reinforced both from the inside and the outside, and has a streamlined shape. The lateral plates, which from the side look like a small seam, have the appearance of a convex ridge inside, which serves as an additional “platform” for attaching muscles.
If we consider the value of pterothorax in the context of ability to fly, then its main function is locomotor. From the outside, it carries wings that allow insects to rise into the air, and from the inside, powerful muscles are attached to it, thanks to which this happens.
Notes
- ↑ Zakhvatkin Yu.A., Course of General Entomology. - M .: Agropromizdat, 1986. - 320 pp., Ill.
- ↑ Shvanvich B.N. The course of general entomology. - M.L. Soviet science. 1949. — 900 pp., Il.
- ↑ Tyshchenko V.P. Fundamentals of the physiology of insects - L., ed. LSU, volume 1, 1976 - 363 p.