A larva (/ˈlɑːrvə/; pl.: larvae /ˈlɑːrv/) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase of their life cycle.

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Larva of the Papilio xuthus butterfly

A larva's appearance is generally very different from the adult form (e.g. caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. In the case of smaller primitive arachnids, the larval stage differs by having three instead of four pairs of legs.[1]

Larvae are frequently adapted to different environments than adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments, but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population.

Animals in the larval stage will consume food to fuel their transition into the adult form. In some organisms like polychaetes and barnacles, adults are immobile but their larvae are mobile, and use their mobile larval form to distribute themselves.[2][3] These larvae used for dispersal are either planktotrophic (feeding) or lecithotrophic (non-feeding).

Some larvae are dependent on adults to feed them. In many eusocial Hymenoptera species, the larvae are fed by female workers. In Ropalidia marginata (a paper wasp) the males are also capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae.[4]

The larvae of some organisms (for example, some newts) can become pubescent and do not develop further into the adult form. This is a type of neoteny.[5]

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Eurosta solidaginis Goldenrod Gall Fly larva

It is a misunderstanding that the larval form always reflects the group's evolutionary history. This could be the case, but often the larval stage has evolved secondarily, as in insects.[6][7] In these cases[clarification needed], the larval form may differ more than the adult form from the group's common origins.[8]

Selected types of larvae

More information Animal, Name of larvae ...
AnimalName of larvae
Porifera (sponges)coeloblastula (= blastula, amphiblastula), parenchymula (= parenchymella, stereogastrula)
HeterocyemidaWagener's larva
Dicyemidainfusoriform larva
Cnidariansplanula (= stereogastrula), actinula
Ctenophoracydippid larvae
PlatyhelminthesTurbellaria: Müller's larva, Götte's larva;
Trematoda: miracidium, sporocyst, redia, cercaria;
Monogenea: oncomiracidium;
Cestoda: cysticercus, cysticercoid, oncosphere (or hexacanth), coracidium, plerocercoid
Annelidanectochaete, polytroch
NematodaDauer larva, microfilaria
Sipunculapelagosphera larva
Ectoproctacyphonautes, vesiculariform larvae
Nematomorphanematomorphan larva
Phoronidsactinotroch
Cycliophorapandora, chordoid larva
Nemerteapilidium, Iwata larva, Desor larva
Acanthocephalaacanthor
LociferaHiggins larva
Brachiopodalobate larva
Priapulaloricate larva
Certain molluscs, annelids, nemerteans and sipunculidstrochophore
Certain molluscsveliger
Mollusca: freshwater Bivalvia (mussels)glochidium
Arthropoda: †Trilobitaprotaspis (unjointed), meraspis (increasing number of joints, but 1 less than the holaspis), holaspis (=adult)[9]
Arthropoda: Xiphosuraeuproöps larva ("trilobite larva")
Arthropoda: Pycnogonidaprotonymphon
CrustaceansGeneral: nauplius, metanauplius, protozoea, antizoea, pseudozoea, zoea, postlarva, cypris, primary larva, mysis
Decapoda: zoea
Rhizocephala: kentrogon
Insecta: Lepidoptera (butterflies and moths)caterpillar
Insecta: Beetlesgrub
Insecta: Flies, Bees, Waspsmaggot
Insecta: Mosquitoeswriggler
Insecta: Orthoptera (crickets and grasshoppers), Odonata (dragonflies and damselflies), Hemiptera (true bugs)nymph
wriggler]]
Deuterostomesdipleurula (hypothetical larva)
Echinodermatabipinnaria, vitellaria, brachiollaria, pluteus, ophiopluteus, echinopluteus, auricularia
Hemichordatatornaria
Urochordatatadpole (does not feed, technically a "swimming embryo")
Fish (generally)Ichthyoplankton
Fish: Petromyzontiformes (lamprey)ammocoete
Fish: Anguilliformes (eels)leptocephalus
Amphibianstadpole, polliwog
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Insect larvae

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The larvae of the Hercules beetle (Dynastes hercules) are among the largest of any species of insect
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Campodeiform larva of Micromus sp.

Within Insects, only Endopterygotes show complete metamorphosis, including a distinct larval stage.[10][11] Several classifications have been suggested by many entomologists,[12][13] and following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types:[14][15]

  1. Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization. All Apocrita are apodous. Three apodous forms are recognized.
  2. Protopod larvae – larva have many different forms and often unlike a normal insect form. They hatch from eggs which contain very little yolk. E.g. first instar larvae of parasitic hymenoptera.
  3. Polypod larvae – also known as eruciform larvae, these larvae have abdominal prolegs, in addition to usual thoracic legs. They are poorly sclerotized and relatively inactive. They live in close contact with their food. Best example is caterpillars of lepidopterans.
  4. Oligopod larvae – have well developed head capsule and mouthparts are similar to the adult, but without compound eyes. They have six legs. No abdominal prolegs. Two types can be seen:
    • Campodeiform – well sclerotized, dorso-ventrally flattened body. Usually long legged predators with prognathous mouthparts. (lacewing, trichopterans, mayflies and some coleopterans).
    • Scarabeiform – poorly sclerotized, flat thorax and abdomen. Usually short legged and inactive burrowing forms. (Scarabaeoidea and other coleopterans).

See also

References

Bibliography

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