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Hexapods (Hexapoda) are a group of arthropods that include more than 1,000,000 described species, most of which are insects but a handful of which belong to the lesser-known group, the Entognatha. In terms of sheer number of species, no other group of animals comes close to the hexapods. Hexapods are, in fact, over twice as specious as all other animal groups combined.

Hexapods are mostly a terrestrial group of animals, though some species inhabit freshwater habitats and others live in coastal marine habitats. The one, albiet vast, habitat that hexapods do not live in is the subtidal marine areas (seas and oceans). The success of hexapods in terms of colonizing land is attributed to their body plan (with its strong cuticle covering that provides protection from predators, infection and water loss) and their flying skills.

Another characteristic of hexapods that bolsters their success is what is known as holometabolous development. Holometabolous development refers to the fact that juvenile and adult hexapods of the same species are very different in their ecological requirements. This means that immature hexapods use different resources (such as food or habitat) than the adult of the same species. This opens up more resources for both young and adults and this is thought to be a great advantage.

Hexapods are vital to the communities in which they belong. Nearly two-thirds of all flowering plant species rely on hexapods for polination. Yet hexapods also pose many threats. They can inflict vast crop damage and are known to spread numerous debilitating and fatal diseases in humans and other animals.

The body of a hexapod is made up of three sections, a head, a thorax and an abdomen. The head has a pair of compounds eyes, a pair of antennae, and numerous mouthparts (such as mandibles, labrum, maxilla, and labium). The thorax consists of three segments, the prothorax, the mesothorax and the metathorax. Each segment of the thorax bears a pair of legs (the forelegs, the middle legs and the hind legs). Most adult insects also have two pairs of wings. The forewings are located on the mesothroax and the hindwings are attached to the metathorax.

Although most hexapods have wings, some are wingless throughout their life or lose wings after a certain period in their life cycle. For example, parasitic insect orders such as lice and fleas no longer have wings (although their ancestors had wings). Other groups such as Entognatha and Zygentoma are more primitive hexapods and their ancestors never had wings.

Many hexapods have evolved alongside the plants in a process called coevolution. This process enables both plants and hexapods to interact in ways that can be beneficial to both. Pollination is one example of a coevolutionary adaptation between plant and pollinator in which both parties benefit.

Some species of hexapods act as parasites. In those species of hexapods that are parasitic, they are often only parasitic during a certain time in their life cycle.

Hexapods have great diversity in their diets and modification of their mouthparts to adapt to the various food sources is common. Many hexapods are herbivorous but some are also carnivores, parasites or parasitoids.

Classification:

Animals > Invertebrates > Arthropods > Hexapods

Hexapods are divided into the following basic groups: