larva, independent, immature animal that undergoes a profound change, or metamorphosis, to assume the typical adult form. Larvae occur in almost all of the animal phyla; because most are tiny or microscopic, they are rarely seen. They play diverse roles in the lives of animals. Motile larvae help to disseminate sessile, or sedentary, animals such as sponges, oysters, barnacles, or scale insects. Larvae of parasites may be dispersed by penetrating the skin of new hosts; other parasite larvae live in intermediate hosts that are normally eaten by the final host, in which the adult parasites develop. The larvae of other parasites live in and are dispersed by intermediate hosts such as mosquitoes, gnats, or leeches; when the blood meals are taken from the final host, the parasite larvae are introduced into the blood or skin. Parasitic infections can often be reduced by eliminating the larval hosts.

Vertebrate Larvae

Among vertebrates a number of fishes pass through larval stages; the larva of the eel is interesting because it is flat and transparent. The tadpole, the familiar larva of the amphibian, develops to a considerable size in the relatively hospitable aquatic environment before metamorphosis prepares it for an amphibious or terrestrial life as a frog or toad.

Insect Larvae

In some animals, especially insects, larvae represent a special feeding stage in the life cycle. Some insects pass through more or less wormlike larval stages, enter the outwardly inactive, or pupal, form, and emerge from the pupal case as adults (see pupa). The importance of larvae in the life cycle of insects varies greatly, as does the proportion of the life span spent in larval, pupal, and adult stages. In many insects, the adult life is relatively short, consisting mostly of mating and egg laying, while the larvae live for many months or, in some species, for several years. Insect larvae feed voraciously, necessarily becoming larger than the adult, as considerable energy and material are needed for the profound changes made during pupation. For this reason, insect larvae often cause far more damage to stored crops and textiles than adult insects.

Insect larvae generally have a thinner exoskeleton than the adult; many are white and soft. The characteristic fly larvae are maggots, often developing in decaying plant or animal material. Mosquito larvae are the familiar aquatic wrigglers; they breathe air and are killed by a thin film of oil on the water that prevents contact with air. Maggots and wrigglers are legless, as are all larvae of the insect order Diptera. Beetle larvae, including the whitish forms called grubs and the long brownish wireworms, are quite diverse, but all are equipped with the six legs characteristic of adults. Moths and butterflies have wormlike caterpillars as larvae, each equipped with the six legs characteristic of adults and false legs known as prolegs to support the long abdominal section. Some, like the milkweed worm (the larva of the monarch butterfly), are relatively naked, while other caterpillars are covered by hairy bristles, sometimes equipped with irritating chemicals that can cause intense itching. The young of the social insects (bees, ants, wasps, and termites) are legless but otherwise grublike. Although all social-insect larvae are ultimately dependent on the parent colony for food, they are considered true larvae because they pass through a pupal stage.

larva The stage in the life cycle of an animal, during which it is motile and capable of feeding itself, that occurs after hatching from the egg, and prior to the reorganizations involved in becoming adult. The appearance of the larval form differs markedly from that of an adult of the same species. Larvae are not usually able to reproduce (but see NEOTENY; PAEDOMORPHOSIS). The term is applied loosely to fish, amphibians, all exopterygote and endopterygote insects at this stage of growth and feeding, although the term ‘nymph’ is frequently applied to exopterygotes and to other invertebrates. See also PUPA.

lar·va / ˈlärvə/ • n. (pl. -vae / -vē; -ˌvī/ ) the active immature form of an insect, esp. one that differs greatly from the adult and forms the stage between egg and pupa, e.g., a caterpillar or grub. Compare with nymph (sense 2). ∎  an immature form of other animals that undergo some metamorphosis, e.g., a tadpole. DERIVATIVES: lar·val / -vəl/ adj. lar·vi·cide / -ˌsīd/ n. ORIGIN: mid 17th cent. (denoting a disembodied spirit or ghost): from Latin, literally ‘ghost, mask.’

larva Developmental stage in the life-cycle of many invertebrates and some other animals. A common life-cycle, typified by the butterfly, is egg, larva, pupa (with a protective outer casing), imago (winged adult). The larva fends for itself and is mobile, but is distinctly different in form from the sexually mature adult. It metamorphoses (or pupates) to become an adult. Names for the larval stage in different organisms include maggot for a fly, caterpillar for a butterfly or moth, and tadpole for a toad or frog.

larva (pl. larvae) The juvenile stage in the life cycle of most invertebrates, amphibians, and fish, which hatches from the egg, is unlike the adult in form, and is normally incapable of sexual reproduction (see paedogenesis). It develops into the adult by undergoing metamorphosis. Larvae can feed themselves and are otherwise self-supporting. Examples are the tadpoles of frogs, the caterpillars of butterflies, and the ciliated planktonic larvae of many marine animals. Compare nymph.

larva (lar-vă) n. (pl. larvae) the preadult or immature stage hatching from the egg of some animal groups, e.g. insects and nematodes, which may be markedly different from the sexually mature adult. l. migrans see creeping eruption.
—larval adj.

larva
A. †spectre, ghost XVII;

B. insect in the grub state XVIII. — L., disembodied spirit, ghost, mask; sense B is an application of the sense ‘mask’ (the perfect insect not being recognizable in the larva).

larva •cadaver, slaver •halva, salver, salvor •balaclava, Bratislava, carver, cassava, Costa Brava, guava, Java, kava, larva, lava, palaver •woodcarver •clever, endeavour (US endeavor), ever, forever, however, howsoever, never, never-never, sever, Trevor, whatever, whatsoever, whenever, whensoever, wheresoever, wherever, whichever, whichsoever, whoever, whomever, whomsoever, whosoever •delver, elver •Denver •Ava, caver, craver, deva, engraver, enslaver, favour (US favor), flavour (US flavor), graver, haver, laver, paver, quaver, raver, saver, savour (US savor), shaver, vena cava, waiver, waver •lifesaver • semiquaver •achiever, beaver, believer, cleaver, deceiver, diva, Eva, fever, Geneva, griever, heaver, leaver, lever, Neva, perceiver, receiver, reiver, reliever, retriever, Shiva, underachiever, viva, weaver, weever •cantilever

Larva

A larva is the name of the stage between hatching and adulthood in the life cycle of some invertebrates (animals without a backbone). A sexually immature organism that lives on its own, a larva seldom resembles its final adult form and usually has entirely different life habits.

A larva, like a caterpillar, is sometimes thought to be a complete, separate, sexually mature organism that has a life of its own and produces more caterpillars. On the contrary, a caterpillar is only one stage (the larval stage) between the hatched egg of a butterfly and the adult butterfly itself. This is typical of one of the major characteristics of larvae—they seldom resemble their final adult stage.

There is no better example than that of the fat, slow-moving, hairy caterpillar that spends all its time eating, and the graceful, often beautiful butterfly that flits and darts from flower to flower. Because a butterfly is an invertebrate that undergoes metamorphosis (a total change in its body shape) as part of its development, it must pass through a larval stage (caterpillar) before it can become a sexually mature butterfly. Like the butterfly, moths also live as caterpillars before they reach their adult flying stage. Among several other invertebrates that pass through larval stages are bees, wasps, and beetles (as grubs), flies (as maggots), mosquitoes (as wrigglers), and frogs and toads (as tadpoles).

All these types of larvae are eating machines, since their main goal is to grow and develop as much as possible. For example, caterpillars

have powerful jaws for chewing leaves. They also do not need to move quickly (nor can they), since they often simply attach themselves to their food source. While this makes them vulnerable to predators, they use different strategies to avoid being eaten. Some use camouflage and blend in perfectly with the leaf color of their favorite food. Others arm themselves with prickly hairs that irritate or with sharp spines. Some are poisonous or taste bad. Larvae also seldom eat the same thing or live in the same habitat that they will as an adult. This means that the immature organism does not compete with the adult organism.

At some point in its short life as a larva, the invertebrate will receive a hormonal signal that will trigger the beginning of its metamorphosis into an adult. According to the type of invertebrate, the larva will go through either complete or incomplete metamorphosis. Incomplete metamorphosis has three stages (egg, larva, adult). Complete metamorphosis has four stages (egg, larva, pupa, and adult). Insects like grasshoppers, dragonflies, and termites go through the shorter, three-stage or incomplete metamorphosis. For these insects, the larva are often called nymphs since they actually resemble miniature adults in their larval stage. The nymph or larva changes into an adult by molting or shedding its outer skin several time as its internal systems develop and enlarge.

Complete metamorphosis is much more dramatic since the adult that finally emerges is so drastically different from the organism it used to be. During complete metamorphosis, the larva goes through a resting stage called the pupa, during which all of these changes take place. At the beginning of the pupal stage, the larva attaches itself to something solid, sheds its skin, and forms a tough outer case around itself called a chrysalis. Usually this is a hard shell, but it sometimes can be a silken covering called a cocoon. The changes that go on during pupation consist mostly of breaking down cells and developing new cells. Eventually the adult insect is formed inside the pupa and it escapes from its casing by breaking it open. What emerges is the former larva now transformed into an adult.

About 90 percent of all insects undergo complete metamorphosis. Certain other invertebrates, like sponges, have larval stages as a way of dispersing their offspring. For example, after sexual fertilization (union of male and female sex cells), many sponges develop thousands of tiny, free-swimming larvae that are released to be carried away by currents and to finally settle and attach themselves to the ocean bottom.

[See alsoLife Cycle; Metamorphosis ]