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]
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]
The larvae of the Hercules beetle (Dynastes hercules) are among the largest of any species of insectCampodeiform 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]
Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization. All Apocrita are apodous. Three apodous forms are recognized.
Hemicephalus – with a reduced head capsule, retractable in to the thorax. Found in Tipulidae and Brachycera families.
Acephalus – without head capsule. Found in Cyclorrhapha
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.
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.
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).
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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