The Neoptera infraclass (which in some taxonomies is a superorder) includes insects that can fly and that can flex their wings over their abdomens.
Insects range in size from less than a millimeter to over 18 centimeters (some walkingsticks) in length.
The relationships of insects to other animal groups remain unclear.
Insects are invertebrate animals of the Class Insecta, the largest and (on land) most widely distributed taxon (taxonomic unit) within the Phylum Arthropoda.
Most insects have two pairs of wings located on the second and third thoracic segments.
Insects are the only invertebrate group to have developed flight, and this has played an important part in their success.
Crop damage and insect-borne diseases, such as malaria, have led to many efforts to control insects.
The circulatory system of insects, like that of other arthropods, is open: The heart pumps the hemolymph through arteries to open spaces surrounding the internal organs.
Many insects, especially beetles, are scavengers, feeding on dead animals and fallen trees, recycling the biological materials into forms found useful by other organisms.
Most insects hatch from eggs, others are ovoviviparous or viviparous, and all undergo a series of molts as they develop and grow in size.
Insects possess segmented bodies supported by an exoskeleton, a hard outer covering made mostly of chitin.
Many modern insect genera developed during the Cenozoic; insects from this period on are often found preserved in amber, often in perfect condition.
Some practitioners make great efforts to avoid even accidental injury to insects, such as wearing gauze masks, avoiding or limiting eating during seasons when insects are abundant, and straining water before drinking.
Insects are an integral part of the food web, whether consumer, prey, or predator.
The study of fossilized insects is called paleoentomology.
Other development traits found in various insects are haplodiploidy, polymorphism, paedomorphosis, sexual dimorphism, parthenogenesis, and more rarely hermaphroditism.
Most extant orders of insects developed during the Permian era that began around 270 million years ago.
Some insects communicate via sound, such as the chirps of male crickets to attract females and warn male crickets away from their territories.
Many higher insects have reduced the number of spiracles; the hoverflies have lost all the spiracles on their abdomen.
Their diversity and prominence has led to speculation that the first insects probably emerged earlier in the Carboniferous period, or even in the preceding Devonian.
The beetles are the most numerous insects, with over 400,000 species identified.
A diffuse tissue of cells found throughout the hemocoel of insects, most of all in the abdomen, is called the fat body.
Many insects possess very refined organs of perception.
Insects occupy a critical role in both ecology and human society.
Like some other invertebrates, insects cannot synthesize cholesterol and must receive it from their diet.
Apart from some tantalizing Devonian fragments, insects first appear suddenly in the fossil record at the very beginning of the Late Carboniferous period, Early Bashkirian age, about 350 million years ago.
Insects commonly regarded as pests include those that are parasitic (mosquitoes, lice, bedbugs), transmit diseases (mosquitoes, flies), damage structures (termites), or destroy agricultural goods (locusts, weevils).
The Endopterygota (also called Holometabola) include those insects whose wings develop inside the body, and that undergo a complete metamorphosis (different larval, pupal, and adult stages).
Some insects, like the well-known housefly, have fused all the body ganglions into one big thoracic ganglion.
Insects have an ability to adapt to extreme temperatures, and are even found on glaciers on the world's highest mountains, in the South Pole, and in hot springs.
Insects have also occupied an important historical role in culture and religion.
Insects comprise the most numerous and diverse group of animals, with around 925,000 species described.
So far, there is nothing that suggests that the insects were a particularly successful group of animals before they got their wings.
Some insect species are considered social insects, such as the ant, the bee, and the termite.
Many insects, such as grasshoppers, can potentially reproduce so quickly that they could literally bury the earth in a single season.
A few smaller groups with similar body plans, such as springtails (Collembola), are united with the insects in the subphylum Hexapoda.
Terrestrial arthropods, such as centipedes, millipedes, scorpions, and spiders, are sometimes confused with insects due to the fact that both have similar body plans, sharing (as do all arthropods) a jointed exoskeleton.
Insects are found in nearly all environments on the planet, although only a small number of species have adapted to life in the open ocean, where crustaceans tend to predominate.
The true insects (that is, species classified in the Class Insecta) are also distinguished from all other arthropods in part by having ectognathous, or exposed, mouthparts.
Insects also produce useful substances such as honey, wax, lacquer, and silk.
Historically, insects have been very important as symbols in religions, whether in myths related to the creation of the world or the scarab serving as the most important religious symbol of ancient Egypt.
The origin of insect flight remains obscure, since the earliest winged insects currently known appear to have been capable fliers.
Human attempts to control pests by insecticides can backfire, because important but unrecognized insects already helping to control pest populations are also killed by the poison, leading eventually to population explosions of the pest species.
The winged insects, and their wingless relatives, make up the subclass Pterygota.
Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs.
The Exopterygota (also called Hemipterodea) include insects whose wings develop outside the body, and lack a pupal stage.
According to cultural materialist anthropologist Marvin Harris, the eating of insects is taboo in cultures that have protein sources that require less work, like farm birds or cattle.
Many insects also have a well-developed number instinct, especially among the solitary wasps.
One means of communication is via pheromones, a chemical that affects the behavior of other insects.
The spiracles are equipped with muscle-controlled valves, enabling the insects to open and close them.
Insects use tracheal respiration in order to transport oxygen through their bodies.
The Bible has 120 or more references to insects.
Invertebrate animals commonly called "worms" include annelids (earthworms and marine polychaete or bristle worms), nematodes (roundworms), platyhelminthes (flatworms), marine nemertean worms ("bootlace worms"), marine Chaetognatha (arrow worms), priapulid worms, and insect larvae such as grubs and maggots.
Some of them eat other insects. Some of them eat blood (like mosquitoes). Nectar from plants is also a popular food. And many insects (like cockroaches or ants) will be happy to polish off that cookie you dropped on the floor!
Spiders, scorpions, and similar animals are not insects; they are arachnids. Arachnids are arthropods that have four pairs of legs. Centipedes are also arthropods, but not insects: they are in a subphylum called the Myriapoda.
Unlike vertebrates that have both smooth and striated muscles, insects have only striated muscles. ... Muscles are attached to the body wall, with attachment fibers running through the cuticle and to the epicuticle, where they can move different parts of the body including appendages such as wings.
Fruit flies are the best-studied insects and are considered a model organism, so it goes to reason if they experience nociception other insects may also. Some activists tout these two studies as proof insects feel pain. ... But nociception is not pain. The current definition of pain requires an emotional response.May 25, 2013
There is no intrinsic reason that insects shouldn't experience emotions. Feelings, on the other hand, are a separate issue. ... These are your body's emotional responses. And they can be, but are not necessarily, coupled with the subjective feelings of sadness or fear, respectively.Sep 30, 2016
However, we can have three rather compelling lines of evidence that our six-legged brethren feel pain. First, insects have a nervous system that resembles ours in many ways. ... Insects can even detect stimuli that are outside of our sensory scope.Nov 25, 2011
Most of the animal species found in the rainforest are invertebrates, including insects, arachnids (such as spiders and scorpions), and worms. Amazingly, about one quarter of all animal species that have been named and described by scientists are beetles.