The larva can look completely different from the adult form, for example, a caterpillar differs from a butterfly. The larva has been extended in meaning by zoologists to denote the young of any animal that is hatched after the close of the embryonic stage and must undergo some form of transformation before it resembles the adult.

Larvae often have special larval organs which do not occur in the adult form. The larvae of some species can become pubescent and not further develop into the adult form This is called neoteny. It is a misunderstanding that the larval form always reflects the group’s evolutionary history. It could be the case, but often the larval stage has evolved secondarily, as in insects. In these cases the larval form might differ more from the group’s
common origin than the adult form. The young of insects that resemble the adult after leaving the egg are also sometimes called larvae. Such young are more properly called nymphs.

In certain aquatic forms the nymph is further modified into a form with gills that is called a naiad. Scientific term for the young of any insects that undergo a complete metamorphosis in the course of development into adults. They vary in structure among different insects. The larvae of beetles are called grubs; those of butterflies and moths are known as caterpillars, and the larval forms of certain flies are called maggots. Before becoming adults, the larvae undergo pupal or chrysalis stages. Among some insects the larval
period is far longer than the adult period. The early life stages of most fish species are considerably different to juveniles and adults of their species and are called larvae.

Larvae bear little resemblance to the adult insects; they have no wings or compound eyes and are usually orm like in form. The eggs of such animals contain little nutrient matter, in contrast to the ample yolk of the eggs of animals that are fully formed after hatching. Special names are usually given to the larva of each type of animal. The larvae of invertebrates cause a number of diseases such as hookworm disease and elephantiasis. The larval stages of aquatic invertebrates that lead sedentary, or attached, lives in the adult stage are typically motile and free-swimming. Such larvae are found in sponges, sessile mollusks, and many rotifers and worms. These larvae serve to increase the distribution of the adults. Among flukes, several aquatic larval stages are observed, the first of which is known as the miracidium. The radially symmetrical echinoderms regularly have bilaterally symmetrical larvae. Among the sea squirts and related ascidians, the larvae often show a higher degree of development than the adults, which degenerate to resemble invertebrates. Among true vertebrates, the best-known example of a larval form is the tadpole stage of the frog.

It’s easy to begin your study of an insect’s life history, but it pays to be careful so you don’t select an insect with a very complicated or long life cycle. invertebrates, an immature stage in the life cycle which usually is much smaller than, and morphologically different from, the
adult. In insects with metamorphosis, the larva must become a pupa before reaching adulthood. The larvae of thread worms and nematodes, which are often parasitic on other animals, usually develop within the body of their hosts.