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Stages of Incomplete Metamorphosis

  • Zoology

In this stages of incomplete metamorphosis post we have briefly explained about complete metamorphosis, incomplete metamorphosis in insects, stages of incomplete metamorphosis in insects and examples.

incomplete metamorphosis in insects is a type of metamorphosis in which an insect hatches from an egg and then goes through several nymphal stages. Each nymphal stage looks like a small version of the adult but getting slightly bigger with age. At the final nymphal stage, the insect then moults into adult form.

Complete Metamorphosis

Complete metamorphosis is the type of insect development that includes egg, larva, pupal, and adult stages, which differ greatly in morphology. The lifecycle of butterflies, ants, fleas, bees, beetles, moths, and wasps are examples of the complete metamorphosis.

Incomplete Metamorphosis

Complete Metamorphosis

The female insect lays eggs, which initiates the entire metamorphosis. The larva, the second stage of the entire metamorphosis, hatches from the eggs. In terms of morphology, behaviour, and/or habitat, the larval stage can be very different from the adult stage. 

The larval body is worm-like and soft. The larvae are distinguished by their voracious feeding. Because of this voracious appetite for food, the larval stage grows at a breakneck pace. Larvae moult their skin several times as they grow. Cocoons form around the larvae as the pupal stage begins. 

When the larva is inside the cocoons, it is inactive and does not feed. Their bodies grow larger, with more segments, internal organs, legs, and wings. The pupal stage can last anywhere from 4 days to several months.  The cocoon rupture releases a fully developed larva.

Incomplete Metamorphosis

Incomplete metamorphosis in insects refers to a type of insect development in which gradual changes occur in the insect during the development from the egg to the adult. The three stages of the incomplete metamorphosis in insects are egg, nymph, and adult. The eggs are laid by the female insect. In most cases, the eggs are covered by an egg case, which protects and hold the eggs together.

Incomplete Metamorphosis

incomplete metamorphosis in insects and Complete Metamorphosis

The eggs hatch into younger nymphs. The nymph resembles the adult without wings. The nymph is also smaller than the adult. The nymph eats the same food as the adult. It develops into the adult through a series of molts. It shed its exoskeleton 4-8 times. When it becomes an adult, the molting does not occur. The incomplete metamorphosis in insects occurs in termites, lice, true bugs, grasshoppers, praying mantis, crickets, and cockroaches.

Differences

The change in body form and habits that occurs during an animal’s development cycle is referred to as metamorphosis. Complete metamorphosis and incomplete metamorphosis in insects are two types of insect growth in which the body form of the insect changes throughout its lifecycle. 

From the egg stage to the adult stage, both complete and incomplete metamorphosis in insects occurs. The four stages of metamorphosis are as follows: egg, larva, pupa, and adult. 

The incomplete metamorphosis in insects, on the other hand, consists of three stages: egg, nymph, and adult. The primary distinction between complete and incomplete metamorphosis is that complete metamorphosis includes a very active, ravenous eating larva and an inactive pupa, whereas incomplete metamorphosis in insects includes a nymph that resembles a miniature adult. 

Wasps, ants, and fleas undergo complete metamorphosis, whereas termites, praying mantis, and cockroaches undergo incomplete metamorphosis.

Stages of Incomplete Metamorphosis in Insects

Insects that go through three stages of change in their life cycle (Egg, Nymph, and Adult) have incomplete metamorphosis, whereas complete metamorphosis has four stages. The egg is the first stage of incomplete metamorphosis in insects. During this time, the insect will develop into a nymph.

The nymph is essentially a miniature version of the adult insect. This is similar to how a child resembles his or her parents. Nymphs typically have a thin exoskeleton and do not have wings. They eat the same foods and live in the same house as their parents. When insect nymphs grow in size, their exoskeleton becomes too tight and must be replaced.

When a nymph outgrows its exoskeleton, it goes through a process known as moulting, in which it sheds its old “skin” or exoskeleton. The new “skin” will harden and transform into the new exoskeleton. This will happen several times until the insect reaches adult size.

Examples

Some insects have a significant difference between their larval and adult forms. This is especially true for butterflies and moths, which crawl around as caterpillars in their larval stages before transforming into flying insects with strikingly beautiful wings in many cases.

Not all insects go through such drastic transformations. Several insect classes change very little in appearance as they grow into adults. Insects such as cockroaches and dragonflies are said to go through incomplete metamorphosis in insects.

Cockroaches

Blattaria is the insect order that includes all cockroach species. Cockroaches are found in over 4,000 different species in forests and human residences. Cockroaches emerge at night to feed on virtually anything that is no longer alive. Although life expectancy varies, the average is two years. Female cockroaches, which are larger than male cockroaches, can reproduce multiple times during their lifetime. Females usually produce an egg case, which they keep in their abdomens. The egg case can produce up to 40 offspring. Roaches go through a series of moults and growth stages after hatching from eggs. Each moult results in a larger version of the insect. The final molt produces the form that possesses wings and reproduces.

Earwigs

The term “earwig” comes from the myth that earwigs crawl into the ears of sleeping people. These brownish insects are members of the order Dermaptera. The length of the species, which includes both winged and wingless varieties, ranges from 10 to 50 mm. The earwig’s most distinguishing feature, the pincers or cerci, differs between genders, with males having more curved cerci. Earwigs have two sets of wings, one on top of the other. Earwigs prefer dark, moist environments. The insects emerge at night to feed on both dead and living plants and animals. After mating, females retain sperm in their bodies for later fertilisation.

Hemiptera

The order Hemiptera includes over 80,000 species of true bugs in the Class Insecta. Members typically have two sets of wings, but some have reduced wings or no wings at all. Bugs have mouths that are designed to puncture and slurp liquids like sap. After hatching from their eggs, bugs go through five nymph stages before reaching adulthood. Many of the agriculturally damaging bugs, such as aphids, are members of the Order Hemiptera.

Mantodea

The familiar praying mantis is a member of the Order Mantodea. Over 200 nymphs can hatch from a single egg case. The body is divided into three sections: a triangle-shaped head, a thorax, and an abdomen. Following a series of nymph formations, an adult emerges, which may or may not resemble the nymphs.

Normally, mantids prey on other insects. Hungry mantids will eat one another if there isn’t enough food. During the mating season, females frequently cannibalise males. To avoid predators, the insects rely heavily on camouflage. Mantids use their long, broad front limbs to catch and hold prey and mates quickly. Farmers love mantids because they eat pesky agricultural pests.

Odonata

Dragonflies and damselflies are distinguished by their elongated, slim abdomens and two pairs of translucent wings. These insects, which are members of the Order Odonata, number over 5,000 species and can be found all over the world. Males of certain species use territoriality for two reasons: to ensure food availability and to entice females.

The eggs are laid in the water by females. The eggs hatch into naiads, which have gills to help them survive in the water. Tadpoles, worms, and shelled creatures that live in the water are eaten by naiads. Adults eat other flying insects, such as mosquitoes. Dragonflies and damselflies catch food by extending lip-like structures called labia, which wind around or pierce through prey and pull the captives toward waiting mouths. Humans benefit from the Order Odonata’s predation on pesky insects.

Orthoptera

Orthoptera includes crickets, grasshoppers, katydids, and locusts. Orthopterans begin life as eggs, develop into nymphs, and then mature into adults that have the body structure of nymphs. The species has two pairs of wings, with the outer, more robust set protecting the inner, more delicate set. The hind legs, which are used for hopping, appear to be more powerful than the front legs. Males of some Orthoptera species announce mating readiness by making distinctive twittering sounds caused by stroking wing against wing or hind leg against wing. Farmers are generally concerned about orthopterans because different species feed on plants.

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