Insects information with pictures
The group of insects, form a class of invertebrates included in the phylum of the Arthropods and in the subphylum of the Hexapods. Its general characteristics include a chitin exoskeleton, a body divided into three parts (head, thorax and abdomen), three pairs of articulated legs, compound eyes and a pair of antennae.
They are one of the most diverse animal species on the planet and include more than one million species, representing more than half of the total living organisms known. They can be found in practically any habitat, although the least frequent for them is the ocean, where another type of arthropod, the crustaceans, dominates.
Characteristics of insects
Among the characteristics of the insects it is noteworthy that their morphology does not differ too much with respect to that of other arthropods. In the head are its two antennas with sensory functions, its two compound eyes and in some cases also three simple ocelli. Its mouthparts are on the underside of the head and are formed by an upper lip (labro), two jaws, two maxilas and a lower lip. The thorax has six articulated limbs and in some species two or four wings. In the abdomen most of the animal’s devices are concentrated: digestive, respiratory, excretory and reproductive.
The digestive system of insects consists of a tube known as a alimentary canal that goes from the mouth to the anus. It is divided into three sections: the previous, the middle and the later. The first is the oral cavity, pharynx, esophagus, crop and proventriculus. In it the first steps of enzymatic and mechanical digestion take place. In the middle section most of the absorption of nutrients through the microvilli occurs. In the back the undigested substances bind to the uric acid secreted by the excretory system and form the fecal balls.
The respiratory system of the insects is tracheal and consists of tubes and bags through which the gases are diffused or actively pumped until they reach the organs directly. As a consequence, the circulatory system is not required to transport oxygen and therefore is very reduced in insects. The size of the insects has been greatly influenced by the respiratory system, which decreases in effectiveness as the size of the animal increases.
The nervous system of the insects is formed by a central nervous cord and by the brain, located in the head and quite developed. In each segment of the insects are a pair of nerve ganglia, although some species have them fused. Insects have fairly developed sensory organs, although they vary according to the species. Many can pick up light, chemical stimuli, vibrations, certain ranges of sound and some may even feel pain.
The feeding of insects is varied, some species feed on plants, others on animals (whole or parts of them like blood), others are omnivores and some are saprophytes.
Reproduction in insects is usually sexual, with individuals of different sexes and usually distinguishable by morphological features. However, in some cases they can reproduce by parthenogenesis or be hermaphroditic. In most cases, the offspring are born through eggs, however the number and shape of these eggs varies greatly depending on the species. In most insects the fertile stage of the females is very short and is capable of generating many offspring in a very short time.
The development of the offspring is indirect, since they undergo metamorphosis until they become adult individuals. The degrees of this metamorphosis are different according to the species: in some, the offspring only differ from adults in size and sexual maturity, while others go through several larval stages before fully developing.
Classification of insects
Being such a diverse class, the classification has not been easy and still today there is some controversy. To not go into detail in the intricate relationships between the different orders, we are simply going to list the most important orders:
The Odonatos are the dragonflies and the damselflies. They are distinguished from most insects in that they can not bend their wings over the abdomen. They are considered more primitive and have an incomplete metamorphosis.
In the group of the Blatodeos are the cockroaches. They have incomplete metamorphosis, have a flattened body and measure between 3 and 7 cm. They have very small compound eyes, they are omnivorous and they have two pairs of wings.
The Orthoptera includes crickets, grasshoppers and locusts. They are characterized by having the third pair of legs adapted to perform jumps.
In the order of the Ftirápteros are lice. They are insects without wings and external parasites of higher animals such as mammals and birds. They feed on remains of skin, feathers or blood of the host.
The Coleoptera is the order of the Animal kingdom with the largest number of species, more than 375,000. Its common name is that of beetles, they have a great diversity of forms and are adapted to almost all habitats.
Diptera are characterized by having only one pair of wings, since the other pair has been reduced and serves to maintain balance. It includes more than 150,000 species, including flies, mosquitoes and horse flies.
The group of lepidoptera integrates butterflies and moths. Most species are nocturnal. They have complete metamorphosis going through a larval phase known as a caterpillar.
The group of Hymenoptera Includes animals as common as ants, bees and wasps. They present complete metamorphosis and it is common for them to reproduce by parthenogenesis. There are many species that are social and live in societies with different castes as is the case of the individual with superior hierarchy, the queen, there are also the workers and drones.