External structure of an insect. External structure of insects: types, description, features. Diversity of insects External structure of insect wings
In this tutorial we will get acquainted with the main parts of the structure of insects, which are presented in illustrated form.
Butterfly head Stag beetle head Grasshopper head
with complicated eyes,
tendrils and sucking
oral apparatus
Insect antennae
Wings of insects Beetle - jumping beetle from the ventral side Legs of insects
Breasts and appendages
ABDOMEN AND ITS APPENDICES
The structure of insect integument
Internal structure of insects (female black cockroach)
Insect circulatory system
Digestive system of insects
Nervous system of insects (Feature of insects - giant nerve cells)
Respiratory system of insects
Insect reproductive system
Incomplete metamorphosis of insects (three stages - egg, larva, adult insect)
Complete metamorphosis of insects (four stages of development - egg, larva, pupa, adult insect)
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INSECT EGGS. An insect egg is a cell ranging in size from 0.02 to 10 mm or more. In addition to the cytoplasm and nucleus, it contains the yolk, which is necessary for the nutrition and development of the embryo. The outside of the egg is covered with a shell - the chorion. Under the chorion there is a vitelline membrane. On the surface of the chorion there is a hole for the passage of sperm. Insect eggs can have any shape, except perhaps egg-shaped.
▼ INSECT PUPAPAS
INSECT LARVA
Worker ants are the guardians of honey. Honey ant foragers fill the abdomen of individual young workers with nectar. The abdomen swells to the size of a grape. In times of famine, nest members receive food from honey keepers
STRUCTURE DIAGRAM OF THE INNER CONE OF THE NEST OF THE RED FOREST ANT
In the inner cone, the juveniles develop, for which workers are responsible.
1. There are workers on the outer dome. Their crops are filled with food, which they exchange among themselves and feed the queen and the larvae.
2. Eggs laid by the queen. Workers lick them and wash them with liquid food.
3. Workers feed protein food to larvae of different ages. The larvae do not dirty their “kindergarten” - after all, their midgut is closed and waste accumulates.
4. Each larva, having completed development, pupates in a cocoon.
5. Workers usually emerge from the cocoons. But in the summer, winged females and males emerge from them and leave the nest.
Scheme of family relationships between orders of insects
(extinct orders are marked with a + sign).
Internal structure of the lancelet
1. External building.
2. Internal structure.
About 1 million species are known. Habitats are varied.
1. External construction
The body of insects is divided into three tagmas: head (cephalon), thorax
(thorax) and abdomen (abdomen).
Head
Consists of an acron and 4 (according to some sources 5 or even 6) segments. It is covered with a chitinous capsule and is movably connected to the thoracic region. There are three types of positioning of the head relative to the body: prognathic, hypognathic and opisthognathic. The head capsule has several sections. The anterior facial part is occupied by the fronto-clypeal section. It consists of the frontal (frons) - frontal sclerite and clypeus (clypeus). The upper lip (labrum) is attached to the clypeus. The second section is the parietal. It consists of two parietal (vertex) sclerites and an occipital (occiput). The occiput is surrounded by the foramen magnum. The lateral sections are located under the compound eyes and are called cheeks (genae).
On the head there are eyes (complex, sometimes simple) and antennae of various structures, as well as mouthparts. The mouthparts of insects vary. Variation in structure is associated with the variety of food consumed by these animals. The initial type of oral apparatus is gnawing (orthopteroid). It is found in insects of many orders (cockroaches, Orthoptera, dragonflies, beetles, etc.). It consists of the following elements: upper lip, mandibles, maxillae, lower lip and hypopharynx. The lapping (bees, bumblebees) is formed by the upper lip, mandibles, in the maxilla the outer chewing blade (galea) is developed and elongated, which forms the upper and part of the lateral surface of the proboscis, the lower lip is represented by an elongated palp (palpi), which forms the lower and part of the lateral surface of the proboscis . Inside the proboscis there is a tongue formed by the internal (glossae) lobes of the lower lip. The sucking mouthparts (Lepidoptera) include the upper lip; in a few
1. External structure
vitels (toothed moths) mandibles, lower lip in the form of a small platform with palps, proboscis formed by elongated external chewing lobes of the maxillae. The piercing-sucking mouthparts (mosquitoes, bedbugs) include the entire set of oral limbs, but they have lost their original shape, most of them have turned into stilettos, which are used to pierce the integument of animals and plants. The lower lip in this device serves as a case. The licking (filtering) mouthparts are characteristic of flies; the labellum of the lower lip are well developed, mandibles and maxillae are absent.
Thoracic region
Formed by 3 segments, locomotor organs are associated with it: legs and wings. The limb of an insect consists of a coxa, trochanter, tibia, tarsus, and pretarsus. There are several types of limbs. The wings are located on the second (mesothorax) and third (methothorax) segments. There are usually 2 pairs of wings, less often (dipterans, fan wings) 1 pair. The second, in this case, is small in size and transformed into halteres. The wings are lateral folds of the integument, originating from the paranotum. They are two-layered, nerves, tracheas, and hemolymph pass through them. The following types of wings are distinguished: mesh, membranous, rigid (elite), semi-rigid (hemieliter). The wings have a system of longitudinal and transverse veins. The longitudinal veins of the wing are: costal (C), subcostal (Sc), radial (R), medial (M), cubital (Cu) and anal (A). In flight, insects use either one or both pairs of wings. Depending on which pair of wings is used in flight, insects are divided into bimotor, anterior- and rear-motor. Many insects, being dipterous, fly on one pair of wings. This phenomenon is called flight dipterization.
Abdominal
Segmented, most of the insect’s internal organs are connected to it. The maximum number of segments in a department is 11, usually there are fewer. The abdominal segment is formed by tergite, sternite and pleural membranes. The abdomen is devoid of real limbs; some insects have modified ones: cerci, styli, ovipositors, sting, jumping fork.
Veils
Represented by the cuticle, hypodermis and basement membrane. The cuticle includes the epicuticle and procuticle. The procuticle consists of two
LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS
1. External structure
layers: exocuticle and endocuticle. The hard body cover limits the growth of the insect. Molting is typical for insects. The integument bears appendages. They are divided into structural and sculptural. The color of the insect is associated with the integument. Coloring is divided into chemical (pigment) and structural (physical). The significance of color for an insect is direct (impact on internal processes) and indirect (impact on other animals). Types of coloring: cryptic - coloring of a resting pose, warning, scaring, mimicry. Derivatives of the hypodermis are wax glands, odorous glands, poisonous glands, varnish glands and others.
2. Internal structure
Muscular system
It is characterized by complexity and a high degree of differentiation and specialization of its individual elements. The number of muscle bundles often reaches 1.5–2 thousand. According to histological structure, almost all insect muscles are striated. Muscles are divided into skeletal (somatic), which ensure the mobility of the body and its individual parts in relation to each other, and visceral (internal). Skeletal muscles are usually attached to the inner surfaces of the cuticular sclerites. There are four groups of somatic muscles: head, pectoral, wing and abdominal. The wing group is the most complex; the muscles of this group in Hymenoptera, Diptera and some others are capable of an extraordinary frequency of contractions (up to 1000 times per second); these are the so-called asynchronous muscles. This frequency of contractions is associated with the phenomenon of multiplication of the response to stimulation, when a muscle responds to one nerve impulse with several contractions. Visceral muscles are connected to internal organs.
Fat body
It is a loose tissue penetrated by tracheae. Color is variable. Functions: accumulation of nutrients, absorption of metabolic products, oxidation of the fat body produces metabolic water, which is especially important in conditions of moisture deficiency. There are four categories of cells in the fat body: trophocytes (the most numerous, they accumulate nutrients), urate cells (uric acid accumulates), mycetocytes (they contain symbiotic microorganisms) and chromocytes (cells contain pigment).
LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS
2. Internal structure
Body cavity
The body cavity of insects, like other arthropods, is mixed. It is divided by diaphragms into 3 sinuses: the upper (pericardial), which houses the heart, the lower (perineural), which houses the abdominal nerve chain, and the visceral sinus occupies the largest volume. The digestive, excretory, and reproductive systems are connected to this sinus. The respiratory system is located in all sinuses of the body cavity.
Digestive system
Three sections: foregut, midgut and hindgut. Between the foregut and midgut there is a cardiac valve, and between the midgut and hindgut there is a pyloric valve. The foregut is represented by the pharynx, esophagus, goiter, and mechanical stomach. Depending on the food consumed, variations in the structure are possible: there is no goiter or stomach. The crop is a temporary place for food; digestion partly occurs here; The function of the stomach is to grind (grind) food. The pharynx of insects that feed on liquid food is muscular and functions as a pump. The salivary glands open into the oral cavity, usually near the base of the lower lip. The enzymes contained in saliva provide the initial stages of digestion. In blood-sucking insects, saliva contains substances that prevent blood clotting - anticoagulants. In some cases, the salivary glands change their function (in caterpillars they turn into spinning glands). Digestion and absorption of food occurs in the middle (small) intestine. In some insects (cockroaches, etc.), several blind protrusions of the intestine flow into the initial part of the intestine - pyloric appendages - they increase the absorption surface. The walls of the midgut form folds - crypts. The type of digestive enzymes depends on the feeding regime of the insects. The secretion of enzymes in insects is holocrine and merocrine. The epithelium of the midgut in many insects secretes a peritrophic membrane around the intestinal contents, the role of which is important in the processes of digestion and absorption of nutrients. In addition, it protects the epithelium of the midgut from mechanical damage. The hind (rectum) intestine is often quite long and is divided into several sections. This is where most insects have rectal glands. Functions of the department: formation and removal of excrement, absorption of water from the food mass, digestion of food with the help of symbionts (typical of the larvae of some types of insects). The intestinal sections are separated by valves that prevent the backflow of food. The anterior and middle sections are separated by the cardiac valve, the middle and posterior sections by the pyloric valve.
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insect body
The insect's body consists of three parts: the head, thorax and back. On the head, 6 segments have merged together and are not noticeable at all. The chest consists of 3 segments. The back part is usually made of 10, on the sides of which there are breathing holes.
Insect skeleton
Insects are invertebrate animals, therefore the structure of their body is fundamentally different from the body structure of vertebrates, which includes humans. Our body is supported by a skeleton consisting of the spine, ribs, and bones of the upper and lower limbs. Muscles are attached to this internal skeleton, with the help of which the body can move.
Insects have an external rather than an internal skeleton. Muscles are attached to it from the inside. A dense shell, the so-called cuticle, covers the entire body of the insect, including the head, legs, antennae and eyes. Movable joints connect numerous plates, segments and tubes found in the insect's body. The cuticle is similar in chemical composition to cellulose. Protein gives extra strength. Fats and wax are part of the surface of the body shell. Therefore, the insect shell is durable, despite its lightness. It is waterproof and airtight. A soft film forms on the joints. However, such a durable body shell has a significant drawback: it does not grow with the body. Therefore, insects have to periodically shed their shells. During its life, an insect changes many shells. Some of them, such as silverfish, do this more than 20 times. The insect's shell is insensitive to touch, heat and cold. But it has holes through which, using special antennae and hairs, insects determine temperature, odors and other characteristics of the environment.
The structure of insect legs
Beetles, cockroaches and ants run very fast. Bees and bumblebees use their paws to collect pollen into “baskets” located on their hind paws. Praying mantises use their front legs to hunt, pinching their prey with them. Grasshoppers and fleas, escaping from an enemy or looking for a new owner, make powerful jumps. Water beetles and bedbugs use their legs to paddle. The mole cricket digs passages in the ground with its wide front paws.
Although the legs of different insects look different, they have a similar structure. The tarsus in the coxa is attached to the thoracic segments. This is followed by the trochanter, femur and tibia. The foot is divided into several parts. At its end there is usually a claw.
Insect body parts
Hairs- microscopic sensory organs protruding from the cuticle, with the help of which insects come into contact with the outside world - they smell, taste, hear.
Ganglion- a knot-shaped accumulation of nerve cells responsible for the activity of individual parts of the body.
Larva- the early stage of insect development, following the egg stage. Variants of larvae: caterpillar, worm, nymph.
Malpighian vessels- excretory organs of an insect in the form of thin tubes that extend into the intestine between its middle section and the rectum.
Pollinator- an animal that transfers pollen from one flower to another of the same species.
Oral apparatus- specially designed for biting, stabbing or licking, organs on the head of an insect, with which they take food, taste, crush and absorb it.
Segment- one of several components of the insect's body. The head consists of 6 practically fused segments, the chest - of 3, the back - usually of 10 clearly distinguishable segments
Shell change- a repeatedly repeated process in the life of an insect; it sheds its old shell in order to grow. In place of the old shell, a new one is gradually formed.
Mustache- thread-like antennae on the insect's head. They perform the functions of sensory organs and serve to obtain olfactory, gustatory, tactile and even auditory sensations.
Compound eye- a complex insect eye, consisting of individual ocelli, the number of which can reach several thousand.
Proboscis- the oral apparatus of piercing-sucking or licking-sucking insects, such as bedbugs, mosquitoes, flies, butterflies and bees.
Exuvia- the old shell of an insect, which it sheds when hatching.
Insects- our constant companions in life. No matter how the operating rooms are sterilized, at least some fly will fly in, and in houses there are always large numbers of them... For robotics engineers, insects are an inspiration, because only they can move on any surface, but repeating this in an artificial model is very difficult.
Like others, insects have an external (exo-) skeleton consisting of chitin. Often growths are observed on the integument of the body - hairs, horny formations, scales, etc.
Body: head, separate chest and abdomen. 3 pairs of walking legs. Most insects have wings(usually 2 pairs).
Features of the internal structure of insects
There are terrestrial insects, and there are also aquatic representatives, so there are differences in respiratory system:
- in aquatic insects, breathing occurs over the entire surface of the body;
- in terrestrials - respiratory organs - trachea.
Circulatory system: open circulatory system , insect blood is called hemolymph. The main vessel containing hemolymph stretches along the length of the insect in the dorsal part. The back of this vessel contains the “heart” - several pulsating chambers connected in series with each other.
Digestive system:
1. A very interesting oral apparatus - it is different for different species:
- gnawing- in those insects that eat solid food, or this food must be obtained (gnawed);
- sucking (piercing-sucking) - for receiving liquid food (butterflies and mosquitoes);
- musky (and gnawing and sucking, like flies)
2. A system consisting of the stomach, intestines, rectum and anus.
Excretory system:malpighian vessels(as in arachnids).
Features of the structure of the nervous system of insects and sensory organs:
Insects have very intense movement, and not chaotic, but quite purposeful, so such movement must be well coordinated. Insects already have a real nervous system - ganglion, consisting of three sections - the ganglion, the ventral nerve cord, and the network of neurons throughout the body.
- antennae (antennas) - organs of touch;
- eyes - can be faceted (complex) or simple, but then there should be several of them.
- insects perceive and distinguish odors well (their basis for communication is the release and recognition of various chemicals).
Reproductive system:
Insects are dioecious. Fertilization is mainly internal.
Development occurs as
Insects are very closely related to many other organisms on Earth.
They are irreplaceable pollinators and food for animals.
A typical representative of the class Insects are Khrushchev May (Melolontha melolontha). The body length reaches from 5 to 60 mm, the wingspan does not exceed four centimeters.
Features of the external structure
Body parts - head, chest and abdomen, each of which performs its own functions. Chairman formed from 6 segments that completely merge. The head has antennae, eyes and mouthparts. The antennae, which are called antennae or siblings, are one pair. In beetles they are lamellar and perform the function of an olfactory organ. The mouth has three pairs of organs: upper jaws (mandibles), lower jaws (maxilla) and upper and lower lips. These organs form gnawing mouthparts. There are projections on the lower jaws and lower lip - palps, which serve as organs of touch and taste. Along with the antennae there are complex (faceted) eyes. In insects they can be simple or complex.
Depending on the type of food, the mouthparts of insects are modified, which leads to the formation of different types of mouthparts:
gnawing mouthparts - oral organs, which include upper And lower lips, upper And mandibles(e.g. grannies, beetles, cockroaches, orthoptera, termites, ants)
gnawing-licking oral apparatus- oral organs in which the lower lip and lower jaws form proboscis, A upper jaws lost chewing function and participate in the construction of honeycombs (bees, bumblebees)
sucking mouthparts - mouth organs have been transformed into proboscis, which is adapted to feeding on nectar from flowers (butterflies)
piercing-sucking mouthparts- oral organs in which the lower lip forms proboscis for sucking liquids, and the upper and lower jaws are turned into long, spiny ones stilettos for piercing body coverings (bugs, aphids, lice, some dipterans).
Some adult insects (silkworms, gadflies) do not feed, so their mouthparts do not function and are very reduced.
Thoracic region consists of three segments (prothorax, mesothorax and metathorax), which have organs of movement - legs and in winged insects - wings. On each segment of the chest there is one pair of limbs, and therefore in insects 3 pairs of walking legs, which is why they are also called hexapods (six-legged). In other insects, these limbs can perform other functions and therefore the following types are distinguished: jumping, swimming, grasping, digging, running, and the like. Two pairs of wings are attached to the second and third segments of insects. Wings are folds of integument, the walls of which are built from the upper and lower layers of epithelial cells covered with a cuticle. Between these layers there is a gap with hemolymph. The supporting frame of the wing is formed by a system of longitudinal and transverse thickenings called veins. In beetles, the first pair is modified into hard elytra. Elytra- modified fore wings that protect the membranous wings from damage when the insect is not flying.
Abdomen formed by a different number of segments (no more than twelve) and contains the bulk of the internal organs. This section is devoid of limbs, has openings of the tracheal system - spiracles, and ends with an ovipositor.
Veils are represented by the hypodermis and chitinous cuticle with a waxy film that prevents the evaporation of water. On the body of an insect there are numerous hairs that perform the function of organs of touch, create an air layer that protects the body from water during rain, from overheating, determine coloring, and the like. The ducts of odorous glands open onto the surface of the body, which help individuals find each other during reproduction. In other insects there may be poisonous (in hairy caterpillars), wax (in bees), silk (in butterfly larvae) and other glands.
Features of the internal structure and life processes
Digestive system consists of the anterior (oral cavity with salivary glands, pharynx, esophagus, stomach), middle (midgut with pyloric appendages, without liver) and posterior (hindgut with anus) sections. Khrushchev eats plant foods, so the outgrowths of its intestines contain symbiotic microorganisms that secrete enzymes for digesting fiber. In larvae, the intestine is relatively long and food is retained in the body for a long time. Absorption of water in order to prevent its loss occurs in the hindgut with the help of the rectal glands.
Respiratory system - tracheal type. A system of tracheal tubes branches throughout the body, which open on the abdomen with dichals - stigmas (on one segment - a pair). Air moves in this system due to diffusion and abdominal movements.
Circulatory system open The heart is tubular, located in the dorsal part of the abdomen.
System fluid - hemolymph- colorless and does not participate in the transportation of gases, which is associated with the development of the trachea. It performs functions such as transport of nutrients
Internal structure of the May beetle: A - antennae; B - subpharyngeal nerve ring: B - December ganglia; G - trachea; D - heart; E - ovary; F - Malpighian vessels; WITH - spiracle; AND - goiter; AND - stomach
substances, transfer of metabolic products, distribution of hormones, protection with the help of phagocyte cells from microorganisms, etc. Hemolymph circulation is carried out by contractions of the heart. When the walls of the heart are stretched with the help of muscles, hemolymph enters the heart through the lateral openings (ostia), and when contracted, the valves close the ostia and fluid enters the arteries.
Excretory system represented by Malpighian vessels and the fat body. Malpighian vessels are excretory tubes at the border of the midgut and hindgut. The number of these outgrowths varies from 2 to 150. The fat body is loose connective tissue, which, among other functions, absorbs metabolic products.
Nervous system - nodal chain type, which is characterized by a well-developed “brain” - a suprapharyngeal accumulation of neurons. It is divided into C sections - anterior, middle and posterior. The anterior section is more complex and provides complex forms of behavior. The ventral chain consists of the pidpharyngeal ganglion and, as a rule, 10 thoracic and abdominal enlarged ganglia.
Behavior very complex and is determined by the interaction of unconditioned and conditioned reflexes. Such innate forms of behavior as instincts play a big role for insects.
Endocrine system carries out humoral regulation with the help of hormones that are secreted by the suprapharyngeal and subpharyngeal nodes, brain appendages, etc. Biologically active substances such as ecdysone, that affect shedding, " juvenile hormone"- inhibits maturation pheromones influence members of their own species sexual attractants- attract individuals of the opposite sex during reproduction, etc.
Sense organs - the most diverse, which is associated with the general high level of organization and complex behavior of insects. Basically, these are hair or other creations with a receptor inside: organs of vision - eyes, complex faceted and simple, organs of smell - antennae, organs of taste - on the mouth and other parts of the body, organs of touch - sensitive hairs on the integument of the body, hearing organs ( tympanic organs, chordotonal organs) are located on the abdomen (in grasshoppers - on the legs). In May beetles, as in other flying insects, there are special antennae at the base. Johnston bodies to control the speed and direction of flight.
Reproduction. May beetles, like almost all insects, are dioecious. Fertilization is internal. The sexual dimorphism of the May beetle is expressed in the fact that the antennae of males have seven segments, while females have only six; females have an ovipositor for laying eggs, extended shin legs for burying them in the soil, etc.
Development in the May beetle it is indirect, in which a pupa is observed in the life cycle. Doll - a stage of insect development with complete metamorphosis, in which internal restructuring occurs, as a result of which the insect turns from a larva into an adult. The transformation from egg to adult insect stage is regulated by hormones and continues for several years in the beetle.
Development in most insects is usually indirect, but there is direct:
1) straight (in primary insects without wings, or bristletail)
2) indirect (or development with transformation - metamorphosis):
■ with complete transformation: egg - larva - doll - imago (in Coleoptera, Hymenoptera, Lepidoptera, Diptera, fleas)
■ with incomplete transformation: egg - larva - imago (in Orthoptera, cockroaches, bedbugs).
The biological significance of the transformation is that: a) larvae and adults live in different conditions and therefore do not compete for habitat and food; b) insects have a greater opportunity to survive under unfavorable living conditions (low temperature, lack of food) at one or another less vulnerable stage of development, in general promotes an increase in the number of individuals of the species.
