A larva's appearance is generally very different from the adult form (e.g.caterpillars andbutterflies) 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 astadpoles live almost exclusively in aquatic environments, but can live outside water as adultfrogs. 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 likepolychaetes andbarnacles, 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 eitherplanktotrophic (feeding) or lecithotrophic (non-feeding).
Some larvae are dependent on adults to feed them. In many eusocialHymenoptera species, the larvae are fed by female workers. InRopalidia 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, somenewts) can becomepubescent and do not develop further into the adult form. This is a type ofneoteny.[5]
It is a misunderstanding that the larval form alwaysreflects 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]
The larvae of theHercules beetle (Dynastes hercules) are among the largest of any species of insectCampodeiform larva ofMicromus sp.
WithinInsects, onlyEndopterygotes show complete metamorphosis, including a distinct larval stage.[10][11] Several classifications have been suggested by manyentomologists,[12][13] and following classification is based onAntonio Berlese classification in 1913. There are four main types of endopterygote larvae types:[14][15]
Apodous larvae – no legs at all and are poorly sclerotized. Based onsclerotization. All Apocrita are apodous. Threeapodous forms are recognized.
Hemicephalus – with a reduced head capsule, retractable in to the thorax. Found inTipulidae andBrachycera families.
Acephalus – without head capsule. Found inCyclorrhapha
Protopod larvae – larva have many different forms and often unlike a normal insect form. They hatch from eggs which contain very littleyolk. E.g. firstinstar larvae of parasitic hymenoptera.
Polypod larvae – also known aseruciform 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 iscaterpillars of lepidopterans.
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 withprognathous 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).
^Qian, Pei-Yuan (1999), "Larval settlement of polychaetes",Reproductive Strategies and Developmental Patterns in Annelids, Dordrecht: Springer Netherlands, pp. 239–253,doi:10.1007/978-94-017-2887-4_14,ISBN978-90-481-5340-4
^Sen, R; Gadagkar, R (2006). "Males of the social wasp Ropalidia marginata can feed larvae, given an opportunity".Animal Behaviour.71 (2):345–350.doi:10.1016/j.anbehav.2005.04.022.S2CID39848913.
^Wakahara, Masami (1996). "Heterochrony and Neotenic Salamanders: Possible Clues for Understanding the Animal Development and Evolution".Zoological Science.13 (6):765–776.doi:10.2108/zsj.13.765 (inactive 1 November 2024).ISSN0289-0003.PMID9107136.S2CID35101681.{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
^Nagy, Lisa M.; Grbić, Miodrag (1999), "Cell Lineages in Larval Development and Evolutions of Holometabolous Insects",The Origin and Evolution of Larval Forms, Elsevier, pp. 275–300,doi:10.1016/b978-012730935-4/50010-9,ISBN978-0-12-730935-4
^Moore, R.C. (1959).Arthropoda I – Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha.Treatise on Invertebrate Paleontology. Vol. Part O. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. O121, O122, O125.ISBN978-0-8137-3015-8.
^JOHNSON, NORMAN. TRIPLEHORN, CHARLES A. (2020).BORROR AND DELONG'S INTRODUCTION TO THE STUDY OF INSECTS. CENGAGE LEARNING CUSTOM P.ISBN978-0-357-67127-6.OCLC1163940863.{{cite book}}: CS1 maint: multiple names: authors list (link)
Brusca, R. C. & Brusca, G. J. (2003).Invertebrates (2nd ed.). Sunderland, Mass. : Sinauer Associates.
Hall, B. K. & Wake, M. H., eds. (1999).The Origin and Evolution of Larval Forms. San Diego: Academic Press.
Leis, J. M. & Carson-Ewart, B. M., eds. (2000). The Larvae of Indo-Pacific Coastal Fishes. An Identification Guide to Marine Fish Larvae. Fauna Malesiana handbooks, vol. 2. Brill, Leiden.
Minelli, A. (2009). The larva. In:Perspectives in Animal Phylogeny and Evolution. Oxford University Press. p. 160–170.link.
Shanks, A. L. (2001).An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Oregon State University Press, Corvallis. 256 pp.
Smith, D. & Johnson, K. B. (1977).A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae. Kendall/Hunt Plublishing Company.
Stanwell-Smith, D., Hood, A. & Peck, L. S. (1997).A field guide to the pelagic invertebrates larvae of the maritime Antarctic. British Antarctic Survey, Cambridge.
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