Insect Totally Explained

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among the solitary wasps that provision with a single species of prey. The mother wasp lays her eggs in individual cells and provides each egg with a number of live caterpillars on which the young feed when hatched. Some species of wasp always provide five, others twelve, and others as high as twenty-four caterpillars per cell. The number of caterpillars is different among species, but it's always the same for each sex of larvae. The male solitary wasp in the genus Eumenes is smaller than the female, so the mother of one species supplies him with only five caterpillars; the larger female receives ten caterpillars in her cell. She can in other words distinguish between both the numbers five and ten in the caterpillars she's providing and which cell contains a male or a female.

Light production and vision

A few insects, such as members of the families Poduridae and Onychiuridae (Collembola), Mycetophilidae (Diptera), and the beetle families Lampyridae, Phengodidae, Elateridae and Staphylinidae are bioluminescent. The most familiar group are the fireflies, beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of Arachnocampa (Mycetophilidae, Fungus gnats) glow to lure small flying insects into sticky strands of silk. Some fireflies of the genus Photuris mimic the flashing of female Photinus species to attract males of that species, which are then capture and devoured. The colours of emitted light vary from dull blue (Orfelia fultoni, Mycetophilidae) to the familiar greens and the rare reds (Phrixothrix tiemanni, Phengodidae).
Most insects except some species of cave dwelling crickets are able to perceive light and dark. Many species have acute vision capable of detecting minute movements. The eyes include simple eyes or ocelli as well as compound eyes of varying sizes. Many species are able to detect light in the infrared, ultraviolet as well as the visible light wavelengths. Colour vision has been demonstrated in many species.

Sound production and hearing

Insects were the earliest organisms to produce sounds and to sense them. Soundmaking in insects is achieved mostly by mechanical action of appendages. In the grasshoppers and crickets this is achieved by stridulation. The cicadas have the loudest sounds among the insects and have special modifications to their body and musculature to produce and amplify sounds. Some species such as the African cicada, Brevisana brevis have been measured at 106.7 decibels at a distance of 50 cm (20 in). These calls are also made by other moths involved in mimicry.
   Very low sounds are also produced in various species of Neuroptera, Lepidoptera (butterflies and moths), Coleoptera and Hymenoptera produced by the mechanical actions of movement often aided by special microscopic stridulatory structures.
   Most sound-making insects also have tympanal organs that can perceive airborne sounds. Most insects are also able to sense vibrations transmitted by the substrate. Communication using substrate-borne vibrational signals is more widespread among insects because of the size constraints in producing air-borne sounds. Insects can't effectively produce low-frequency sounds, and high-frequency sounds tend to disperse more in a dense environment (such as foliage), so insects living in such environments communicate primarily using substrate-borne vibrations. The mechanisms of production of vibrational signals are just as diverse as those for producing sound in insects.
   Some species use vibrations for communicating within members of the same species, such as to attract mates as in the songs of the shield bug Nezara viridula while it can also be used to communicate between entirely different species, such as between ants and myrmecophilous lycaenid caterpillars.
   The Madagascar hissing cockroach has the ability to press air through the spiracles to make a hissing noise, and the Death's-head Hawkmoth makes a squeaking noise by forcing air out of their pharynx.

Chemical communication

In addition to the use of sound for communication, a wide range of insects have evolved chemical means for communication. These chemicals, termed semiochemicals, are often derived from plant metabolites include those meant to attract, repel and provide other kinds of information. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well known to have developed in social insects.

Social behaviour

Social insects, such as the termites, ants and many bees and wasps, are the most familiar species of eusocial animal. They live together in large well-organized colonies that may be so tightly integrated and genetically similar that the colonies of some species are sometimes considered superorganisms. It is sometimes argued that the various species of honey bee are the only invertebrates (and indeed one of the few non-human groups) to have evolved a system of abstract symbolic communication (for example, where a behaviour is used to represent and convey specific information about something in the environment), called the "dance language" - the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown.
Only those insects which live in nests or colonies demonstrate any true capacity for fine-scale spatial orientation or "homing" - this can be quite sophisticated, however, and allow an insect to return unerringly to a single hole a few millimetres in diameter among a mass of thousands of apparently identical holes all clustered together, after a trip of up to several kilometres' distance, and (in cases where an insect hibernates) as long as a year after last viewing the area (a phenomenon known as philopatry). A few insects migrate, but this is a larger-scale form of navigation, and often involves only large, general regions (for example, the overwintering areas of the Monarch butterfly).

Care of young

Most insects lead short lives as adults, and rarely interact with one another except to mate, or compete for mates. A small number exhibit some form of parental care, where that'll at least guard their eggs, and sometimes continue guarding their offspring until adulthood, and possibly even actively feeding them. Another simple form of parental care is to construct a nest (a burrow or an actual construction, either of which may be simple or complex), store provisions in it, and lay an egg upon those provisions. The adult doesn't contact the growing offspring, but it nonetheless does provide food. This sort of care is typical of bees and various types of wasps.

Locomotion

Flight

Insects are the only group of invertebrates to have developed flight. The evolution of insect wings has been a subject of debate. Some proponents suggest that the wings are para-notal in origin while others have suggested they're modified gills. In the Carboniferous age, some of the Meganeura dragonflies had as much as a 50 cm (20 in) wide wingspan. The appearance of gigantic insects has been found to be consistent with high atmospheric oxygen. The percentage of oxygen in the atmosphere found from ice core-samples was as high as 35% compared to the current 21%. The respiratory system of insects constrains their size, however the high oxygen in the atmosphere allowed larger sizes. The largest flying insects today are much smaller and include several moth species such as the Atlas moth and the White Witch (Thysania agrippina).
Insect flight has been a topic of great interest in aerodynamics due partly to the inability of steady-state theories to explain the lift generated by the tiny wings of insects.
In addition to powered flight, many of the smaller insects are also dispersed by winds. These include the aphids which are often transported long distances by low-level jet streams.

Walking

Many adult insects use six legs for walking and have adopted a tripedal gait. The tripedal gait allows for rapid walking whilst always having a stable stance and has been studied extensively in cockroaches. The legs are used in alternate triangles touching the ground. For the first step the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, whilst the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle the other legs can be lifted and brought forward in turn and so on.
   The purest form of the tripedal gait is seen in insects moving at speed. However, this type of locomotion isn't rigid and insects can adapt a variety of gaits; for example, when moving slowly, turning, or avoiding obstacles, four or more feet may be touching the ground. Insects can also adapt their gait to cope with the loss of one or more limbs. Cockroaches are amongst the fastest insect runners and at full speed actually adopt a bipedal run to reach a high velocity in proportion to their body size. As Cockroaches move extremely rapidly, they need recording at several hundred frames per second to reveal their gait. More sedate locomotion is also studied by scientists in stick insects Phasmatodea.
   A few insects have evolved to walk on the surface of the water, especially the bugs of the family, Gerridae, also known as water striders. A few species of ocean-skaters in the genus Halobates even live on the surface of open oceans, a habitat that has few insect species.
   Insect walking is of particular interest as an alternative form of locomotion to the use of wheels for robots (Robot locomotion).

Swimming

A large number of insects live either parts or the whole of their lives underwater. In many of the more primitive orders the immature stages are aquatic while some other groups have aquatic adults as well.
   Many of these species have adaptations to help in locomotion under water. The water beetles and water bugs have legs adapted into paddle like structures. Dragonfly naiads, use jet propulsion, forcibly expelling water out of the rectal chamber.
   Some species like the water striders are capable of walking on the surface of water. They can do this because their claws are not at the tips of the legs as in most insects, but recessed in a special groove further up the leg; this prevents the claws from piercing the water's surface film.
   Species that are submerged also have adaptations to aid in respiration. Many larval forms have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies which may be held or trapped in special structures. }} }} }} }} }} Simplified Cladogram of insect groups and very simplified. Note that Apterygota, Palaeoptera and Exopterygota are possibly paraphyletic groups. † signifies an extinct taxon. Apterygota

Monura †

Monocondylia

Archaeognatha=Microcoryphia (bristletails) Dicondylia � * Thysanura=Zygentoma (silverfish)

� Pterygota

� : Paleoptera

   :* Ephemeroptera (mayflies) � :* Palaeodictyoptera †

   :* Megasecoptera † � :* Archodonata †

   :* Diaphanopterodea † � :* Protodonata=Meganisoptera †

   :* Protanisoptera † � :* Triadophlebioptera †

   :* Protozygoptera=Archizygoptera † � :* Odonata (dragonflies, damselflies)

� : Neoptera

� :: Polyneoptera

   ::* Caloneurodea † � ::* Titanoptera †

   ::* Protorthoptera † � ::* Plecoptera (stoneflies)

   ::* Embiidina=Embioptera (webspinners) � ::* Zoraptera (angel insects)

   ::* Dermaptera (earwigs) � ::* Orthoptera (grasshoppers, crickets, katydids)

   ::* Phasmatodea (stick insects) � ::* Notoptera (ice-crawlers & gladiators)

   ::* Blattaria (cockroaches) � :::* Isoptera (termites - included in Blattaria)

   ::* Mantodea (mantids) � :: Paraneoptera

   ::* Psocodea (booklice, barklice) � :::* Mallophaga (chewing lice - in Psocodea)

   :::* Anoplura (sucking lice - in Psocodea) � ::* Thysanoptera (thrips)

   ::* Hemiptera (true bugs, aphids, cicadas) � :: Endopterygota=Holometabola

   ::* Glosselytrodea † � ::* Miomoptera †

   ::* Hymenoptera (wasps, bees, ants) � ::* Coleoptera (beetles)

   ::* Strepsiptera (twisted-winged parasites) � :: Neuropterida

   ::* Raphidioptera (snakeflies) � ::* Megaloptera (alderflies, dobsonflies)

   ::* Neuroptera (lacewings, antlions) � :: Antliophora/Mecopteroidea

   ::* Mecoptera (scorpionflies, hangingflies) � :::* Siphonaptera (fleas - in Mecoptera)

� ::* Diptera (true flies)

   ::* Protodiptera † � :: Amphiesmenoptera

   ::* Trichoptera (caddisflies) � ::* Lepidoptera (butterflies, moths, skippers)

Insects can be divided into two groups, historically treated as subclasses: Apterygota (wingless) and Pterygota (winged). The Apterygota consists of two primitively wingless orders - Archaeognatha (bristletails) and Thysanura (silverfish). Archaeognatha makes up the Monocondylia (based on mandibular morphology) while Thysanura and Pterygota are grouped together as Dicondylia. It is possible that the Thysanura itself isn't monophyletic, with the family Lepidotrichidae a sister group to the Dicondylia (Pterygota + the remaining Thysanura).
   Paleoptera and Neoptera are the winged orders of insects, separated by the presence of sclerites and musculature that allow for folding of the wings flat over the abdomen in the latter group. Neoptera can further be divided into hemimetabolous (Polyneoptera & Paraneoptera) and Holometabolous groups. It has proven particularly difficult to elucidate interordinal relationships within Polyneoptera. Phasmatodea and Embiidina have been suggested to form Eukinolabia. Mantodea, Blattodea & Isoptera are thought to form a monophyletic group termed Dictyoptera. Paraneoptera has turned out to be more closely related to Endopterygota than to the rest of the Exopterygota. The recent molecular finding that the traditional louse orders Mallophaga and Anoplura are derived from within Psocoptera has led to the new taxon Psocodea.
   It is quite likely that Exopterygota is paraphyletic in regards to Endopterygota. Contentious matters include Strepsiptera and Diptera grouped together as Halteria based on a reduction of one of the wing pairs - a position not well-supported in the entomological community. The Neuropterida are often "lumped" or "split" on the whims of the taxonomist. Fleas are now thought to be closely related to boreid mecopterans. Many questions remain to be answered when it comes to basal relationships amongst endopterygote orders, particularly Hymenoptera.

Relationship to humans

Many insects are considered pests by humans. Insects commonly regarded as pests include those that are parasitic (mosquitoes, lice, bed bugs), transmit diseases (mosquitoes, flies), damage structures (termites), or destroy agricultural goods (locusts, weevils). Many entomologists are involved in various forms of pest control, often using insecticides, but more and more relying on methods of biocontrol.
   Although pest insects attract the most attention, many insects are beneficial to the environment and to humans. Some pollinate flowering plants (for example wasps, bees, butterflies, ants). Pollination is a trade between plants that need to reproduce, and pollinators that receive rewards of nectar and pollen. A serious environmental problem today is the decline of populations of pollinator insects, and a number of species of insects are now cultured primarily for pollination management in order to have sufficient pollinators in the field, orchard or greenhouse at bloom time.
   Insects also produce useful substances such as honey, wax, lacquer and silk. Honey bees have been cultured by humans for thousands of years for honey, although contracting for crop pollination is becoming more significant for beekeepers. The silkworm has greatly affected human history, as silk-driven trade established relationships between China and the rest of the world. Fly larvae (maggots) were formerly used to treat wounds to prevent or stop gangrene, as they'd only consume dead flesh. This treatment is finding modern usage in some hospitals. Adult insects such as crickets, and insect larvae of various kinds are also commonly used as fishing bait.
   In some parts of the world, insects are used for human food ("Entomophagy"), while being a taboo in other places. There are proponents of developing this use to provide a major source of protein in human nutrition. Since it's impossible to entirely eliminate pest insects from the human food chain, insects already are present in many foods, especially grains. Most people don't realize that food safety laws in many countries don't prohibit insect parts in food, but rather limit the quantity. 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, especially beetles, are scavengers, feeding on dead animals and fallen trees, recycling the biological materials into forms found useful by other organisms, and insects are responsible for much of the process by which topsoil is created. The ancient Egyptian religion adored dung beetles and represented them as beetle-shaped amulets, or scarabs.
   The most useful of all insects are insectivores, those that feed on other insects. Many insects can potentially reproduce so quickly that if all of their offspring were to survive, they could literally bury the earth in a single season. However, for any given insect one can name, whether it's considered a pest or not, there will be one to hundreds of species of insects that are either parasitoids or predators upon it, and play a significant role in controlling it. This role in ecology is usually assumed to be primarily one of birds, but insects, though less glamorous, are much more significant.
   Human attempts to control pests by insecticides can backfire, because important but unrecognised insects already helping to control pest populations are also killed by the poison, leading eventually to population explosions of the pest species.

Quotations

"Something in the insect seems to be alien to the habits, morals, and psychology of this world, as if it had come from some other planet: more monstrous, more energetic, more insensate, more atrocious, more infernal than our own." � :—Maurice Maeterlinck (1862–1949)

When asked what can be learned about the Creator by examining His work, J.B.S. Haldane said "an inordinate fondness for beetles."

"To understand the success of insects is to appreciate our own shortcomings" —Thomas EisnerFurther Information

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