Ovipositor

Ovipositor

The ovipositor is an organ used by some animals for the laying of eggs. In insects, for example, it consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly. In some of the insect orders, such as the Hymenoptera, Lepidoptera, and Diptera, the organ is used merely to attach the egg to some surface, but in others it is used to deposit the egg in some specially prepared place.

Structure and Function

The ovipositor is a complex structure. It is formed from a pair of appendages on the last abdominal segment. The appendages are modified into a tube that can be extended or retracted. The tube is used to deposit eggs. In some species, the ovipositor is also used for piercing, as in the Ichneumonidae, or for sawing, as in the Tenthredinidae. In these groups, the ovipositor is used to deposit eggs in the bodies or eggs of other insects.

In Different Species

In many insects, the ovipositor is a simple tube, but in some it is a complex structure with various adaptations. For example, in the Hymenoptera, the ovipositor is often modified into a sting. In the Orthoptera (grasshoppers, crickets, etc.), the ovipositor is long and slender, and is used to deposit eggs in the ground or in plant tissues. In the Lepidoptera (butterflies and moths), the ovipositor is short and broad, and is used to attach eggs to plant tissues.

Evolution

The ovipositor has evolved in various ways in different groups of insects. In some, it has become a specialized organ for injecting venom, as in the Hymenoptera. In others, it has become a drill for boring into plant or animal tissues, as in the Ichneumonidae and Tenthredinidae. In still others, it has become a saw for cutting into plant tissues, as in the Cynipidae.

See Also

• Egg (biology)
• Insect morphology
• Hymenoptera
• Lepidoptera
• Diptera

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