Insects are invertebrates that are classified within the phylum of the Arthropods and in the subphile of the Hexapods. Due to their characteristics, insects are one of the most diversified groups of animals in the world, including up to more than half of the known living organisms. Insects inhabit all types of habitats, although the least common is the oceanic one, where arthropods are represented by crustaceans.
The characteristics of insects
The general characteristics of insects are:
- Possess a chitin exoskeleton.
- A body organized in three parts (head, thorax and abdomen).
- Compound eyes
- One by antenas.
- Three pairs of articulated legs.
On the head they have the pair of antennae with sensory functions , the pair of compound eyes and sometimes three simple ocelli. In the lower part of the head, the mouthparts are located with its upper lip (labrum), a lower lip, two maxillae and two mandibles. The thorax has six articulated limbs and, occasionally, one or two pairs of antennae. While most of the insect’s apparatus are found in the abdomen, the digestive, reproductive, excretory and respiratory systems.
The respiratory system is made up of a trachea, which is a system of tubes and sacs, where gases diffuse or are pumped to the organs, so they do not need a circulatory system. There is a relationship between the respiratory system and the size of the insect, whose effectiveness decreases with the size of the animal.
The digestive system of an insect consists of an alimentary canal from the mouth to the anus. This canal is divided into an anterior region (oral cavity, pharynx, esophagus and crop, middle and posterior. Enzymatic and mechanical digestion of food occurs in the anterior region, similar to what happens in the mouth and stomach of humans. The middle region is for the absorption processes of nutrients through the microvilli, analogous to what happens in the small intestine and the first part of the large part of humans and in the later part, undigested substances combine with uric acid. to form fecal balls and be excreted.
Your nervous system consists of a central nervous cord and the brain, located in the head. The nerve cord is segmented, with a pair of nerve ganglia per segment, which are fused in some insects. In addition to this, insects have developed sensory organs, which allow them to capture light, vibrations, detect chemical stimuli, capture sounds or even feel pain, although the type of organ varies according to the species.
The diet varies according to the species , there are those that feed on plants, animals (whole or parts), omnivores or saprophytes.
With regard to reproduction , it is usually sexual, since individuals have separate sexes and are distinguished by their morphological characteristics, other species are parthenogenic and others have hermaphroditic individuals. In most species, females have a very short fertile stage, so they must produce many young in a short period of time . Most of the time, females lay eggs, but their number and shape varies by species.
After their birth, the young have an indirect development , having to undergo a metamorphosis before becoming adults. The metamorphosis process varies according to the species: in some the young only differ in size and sexual maturity with respect to the adult and in others they go through several larval stages.
The classification of insects arouses some controversy, but in general the following orders can be distinguished:
This order includes dragonflies and damselflies. This is considered the most primitive order of insects, they cannot fold their wings on the abdomen and present incomplete metamorphosis.
This order includes cockroaches. They are species with indirect metamorphosis, flattened body, omnivorous and with a pair of wings.
Includes crickets, lobsters and grasshoppers. They have a third pair of legs that is adapted for jumping.
They include lice. They do not have wings and are parasites, feeding on the host’s skin, blood or feathers.
They represent the animal kingdom with the largest number of known species. Includes beetles. This order has a great diversity of forms and is adapted to all habitats.
Includes flies, mosquitoes, and horseflies. They have only one pair of wings, with the other very reduced and used to maintain balance.
Includes butterflies and moths. They have complete metamorphosis and are adapted to nightlife.
It includes ants , bees, and wasps. They have complete metamorphosis and reproduce by parthenogenesis. They are characterized because many of their species are social and are organized in societies with a range of hierarchies.