A cocoon [ kokɔ ː; - Kɔŋ; -Ko ː n] (French: Coque = egg shell, housing) is produced by means of a secretion housing that is designed to protect eggs or young forms of the animals who have built it. If a cocoon to protect the eggs from hatching and the hatchlings produced, it make the parents here. Cocoons, which are necessary for survival of older stages of development, such as the pupa, are manufactured by the therein pups themselves. You can find these cocoons especially in various arthropods ( Arthropoda ), but also in some worms.
Cocoons in arthropods
Cocoons can occur within the arthropods, for example, in insects, arachnids and millipedes. In holometabolous insects are found in addition to those for the protection of the eggs even those that are used for survival of the pupal period until hatching of the imago. The best known are the cocoons made by the larvae of certain butterfly families. Caterpillars produce these by means of a silk glands emerging from liquid which solidifies to threads very quickly in the air. These are spun into cocoon in which the caterpillar to pupa sheds its skin, and then spend the entire pupal therein. The cocoons of silkworms provide the silk. The beetle larvae ( grubs ) of the superfamily Scarabaeoidea ready for the pupal cocoon of a body secretion and earth, they only leave as adult beetles. This is, as the cavity in which transitions pupate boring beetle larvae, called Puppenwiege.
Cocoons are made to protect the eggs, often species-specific forms and are usually referred to as oothecae. Cockroaches ( Blattodea ) and Mantis ( Mantodea ) produce their cocoons known as ootheca by discharged their eggs in one of the females during oviposition, store fixed curing secretion. The cocoons that produce some bugs for their eggs, on the other hand not called oothecae. The females of many water beetles ( Hydrophilidae ) have a spinning apparatus at the end of the abdomen, with which they spin a cocoon for her eggs. This can be attached to water plants or swim as so-called shuttle freely in the water. Even with the most arachnids (Arachnida ), the eggs are wrapped up in cocoons. Some groups of millipedes ( Diplopoda ) produce for their eggs cocoons, which are often like that of the mantis and cockroach called oothecae. The production of cocoons from Schnurfüßern ( Julida ) and Bandfüßern ( Polydesmida ) resembles that of the doll's cradle of Scarabaeoidea. They dress the caves in which they have laid their eggs by a secretion from which hardens the walls. The cocoons of Samenfüßer ( Chordeumatidae ) caused by the Spinning of the eggs in a dream.
Cocoons in worms
To protect the eggs and later the young worms also produce some worms cocoons. With belt worms ( Clitellata ) to the belt ( Clittellum ) is secreted a mucus, which soon will be relatively fixed. From the thus created short hose to the belt worms pull backwards. Upon passing the Gender spores, the eggs are then pressed in. The Wenigborstern ( Oligochaeta ) fertilization takes place during the passage of the seed bag ( seminal receptacle ). The sperm contained herein are also fired in these tube into it, where they fertilize the eggs. In leeches ( Hirudinea ) other forms of fertilization occur. If the worm has pulled the head out of the tube, close the two openings. The result is an often thin-skinned, partially BANDED also with a thicker wall or foam-like cocoon with a protein-rich nutrient solution. In this, the eggs develop into young worms, which eventually hatch.
Oothecae the American cockroach ( Periplaneta americana)