Insect evolution

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Most insects are born from eggs, but some insects are ovoviviparous or viviparous. All types of run during its development and growth of a number of molting. External skeleton consisting of solid cuticle is not smooth growth of the individual. Stripping is a process during which it is too tight and restricting the growth of cuticle replaced always more to undress before creating the current lower cuticle. This process is repeated several times. During dressing chitinous cover on the back of the larva breaks in a somewhat larger, but still soft cuticullar package leaves the current tight shell. After a while the new cuticle to solidify the air, freezes and becomes solid support body.

Some species of insects are called nymphs, young individuals, who in addition to undeveloped wings, allowing them to grow into adulthood, very similar to adults. In this case, an individual passes through a stage in the development of helmets and the gradual development of the adult is called an imperfect transformation (hemimetabolie).

For advanced development groups lack the basics of insect larvae, wings, and before undergoing metamorphosis stage pupae. At this stage, not eat and are at rest with limited possibilities of movement. The cocoon is the reconstruction of the deep internal organs larvae in bodies of adult insects. Such a transformation is called a perfect transformation (holometabolie) and characterized it superorder Endopterygota insects known.

Insects belonging to the suborder, the larvae hatch from eggs in the general form of the worm and the larvae can be divided into five different forms:
  • Eruciforma (caterpillar)
  • Scarbaeiforma (grub)
  • Campodeiforma (oblong, flattening and active)
  • Elateriforma (wireworm)
  • Vermiforma (worm)
Larvae gradually grows and eventually disguise the chrysalis or cocoon, which may be of various kinds. They recognized three basic types of helmets:
  • Mummy cocoon (pupa obtecta), which show the head and antennae sucker
  • Free cocoon (pupa, or pupa libera exarate), which have distinct foundations feet, more or less protruding from their hoods
  • Hood closed (coarctate pupa), which is closed and is evolving in the old larval skin

The pupal occur on land, soil, the vegetation in different parts of plants, the bushes in cocoons arising from the glandular secretions Weaver would result in the oral cavity, or directly from the secretions of the salivary glands. In the pupae stage of insects undergo substantial change, and then appears in the form of adult or imago. Butterflies as an example of insects that undergo complete metamorphosis. Some insects have even developed by hypermetamorfózy.

Other species of insects (parasitic wasps) conducts polyembryony where each fertilized egg can be divided into many (a thousand) individual embryo. Other developmental and reproductive variations include haplodiploidy, polymorphism, paedomorfismus, sexual dimorphism, parthenogenesis and hermaphroditism is very rare.

Source: Wikipedia