Ovipositor

Ovipositor oflong-horned grasshopper(the twocerciare also visible)

Theovipositoris a tube-likeorganused by someanimals,especiallyinsects,for the laying ofeggs.In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typically its form is adapted to functions such as preparing a place for the egg, transmitting the egg, and then placing it properly. For most insects, the organ is used merely to attach the egg to some surface, but for manyparasiticspecies (primarily inwaspsand otherHymenoptera), it is a piercing organ as well.

Some ovipositors only retract partly when not in use, and thebasalpart that sticks out is known as thescape,or more specificallyoviscape,the wordscapederiving from the Latin wordscāpus,meaning "stalk" or "shaft".

In insects

The process of oviposition inDolichomitus imperator:
1. Tapping with her antennae, the wasp listens for the vibrations that indicate a host is present
2. With the longer ovipositor, the wasp drills a hole through the bark
3. The wasp inserts the ovipositor into the cavity which contains the host larva
4. Making corrections
5-6. Depositing the eggs

Grasshoppersuse their ovipositors to force a burrow into the earth to receive the eggs.Cicadaspierce thewoodof twigs with their ovipositors to insert the eggs.Sawfliesslit thetissuesofplantsby means of the ovipositor and so do some species oflong-horned grasshoppers.In the ichneumon wasp genusMegarhyssa,the females have a slender ovipositor (terebra) several inches long that is used to drill into the wood oftree trunks.These wasps are parasitic in thelarvalstage on the larvae ofhorntailwasps, hence the egg must be deposited directly into the host's body as it is feeding. The ovipositors ofMegarhyssaare among the longest egg-laying organs (relative to body size) known.

Thestingersof theAculeata(wasps, hornets, bees, and ants) are ovipositors, highly modified and with associatedvenomglands.They are used to paralyze prey, or as defensive weapons. The penetrating sting plus venom allows the wasp to lay eggs with less risk of injury from the host. In some cases, the injection also introduces virus particles that suppress the host's immune system and prevent it from destroying the eggs.However, in virtually all stingingHymenoptera,the ovipositor is no longer used for egg-laying. An exception is the familyChrysididae,members of the Hymenoptera, in which species such asChrysis ignitahave reduced stinging apparatus and a functional ovipositor.

Fig waspovipositors have specialized serrated teeth to penetrate fruits, butgall waspshave either uniform teeth or no teeth on their ovipositors, meaning themorphologyof the organ is related to the life history.

Members of theDipteran(fly) familiesTephritidaeandPyrgotidaehave well-developed ovipositors that are partly retracted when not in use, with the part that sticks out being the oviscape.Oestridae,another family within Diptera, often have short hairy ovipositors, the speciesCuterebra fontinellahas one of the shortest within the family.

Ovipositors exist not only inwinged insects,but also inApterygota,where the ovipositor has an additional function in gathering the spermatophore during mating. Little is known about the egg-laying habits of these insects in the wild.

In fish

Female bitterlings in the genusRhodeushave an ovipositor in the form of a tubular extension of thegenitalorifice. During breeding season, they use it when depositing eggs in the mantle cavity of freshwatermussels,where their eggs develop in reasonable security.Seahorseshave an ovipositor for introducing eggs into the brood pouch of the male, who carries them until it is time to release the fry into a suitable situation in the open water.

In amphibians

Themarbled newt,orTriturus marmoratus,females participate in parental investment by ovipositing their eggs. They carefully wrap them in aquatic leaves as a form of protection, scattering them throughout a pond to avoid predation. Females are not able to breathe during the oviposition process; therefore, the benefit to wrapping the eggs outweigh the cost of holding their breath.

Images

• 
  A female fly in the familyTephritidae,with the ovipositor retracted and only the scape showing.
• 
  Ovipositing Mexican fruit flies showing the scapes of the extended ovipositors.
• 
  FemaleMegarhyssalaying eggs with her ovipositor.
• 
  Dolichomitussp.laying eggs into a nest ofOsmiasp..
• 
  Leucospis dorsigeralaying eggs into a nest ofOsmiasp..
• 
  A young female ofgreat green bush-cricket(Tettigonia viridissima) the ovipositor is clearly visible.

External links

• Media related toOvipositorat Wikimedia Commons