Why do butterflies undergo metamorphosis

Other species of butterflies have different positions for pupating. The fifth instar eats, grows, and becomes too big for its skin. This final caterpillar instar will molt one more time, but the result of this molt is quite different. The chrysalis generically referred to as a pupa , is not a "resting" stage as many people think. Quite to the contrary, a lot is happening to the pupa! The body of the caterpillar is transforming into an adult butterfly! Wings are fully formed the beginnings of the wings were actually forming underneath the caterpillar's skin before its last molt in the chrysalis.

Antennae are formed and the chewing mouthparts of the caterpillar are transformed into the sucking mouthparts of the butterfly. After approximately 10 to 14 days as a chrysalis, the butterfly is ready to emerge.

When the butterfly emerges from its chrysalis, its wings are small and wet, and the butterfly cannot yet fly. The butterfly must pump fluids from its abdomen through the veins in its wings, which causes the wings to expand to their full size. Next, the wings must dry and the butterfly must exercise flight muscles before it can fly.

Papilio polytes …adult. The main job of an adult butterfly's life is to reproduce. After a female butterfly mates, she searches for the proper host plant to lay her eggs, and the cycle begins again. Butterflies and moths go through the same stages in their metamorphosis with one difference. During this period, the larval brain stimulates the release of enzymes which dissolve most of its tissues into their constituent proteins through a process called histolysis.

Then a group of specialised cells called histoblasts proceed to reconstruct the broken-down caterpillar body into that of a butterfly or a moth. A few years ago, Martha Weiss and her group at Georgetown University discovered that aversive memories formed in the tobacco hornworm caterpillar Manduca sexta persisted throughout metamorphosis and were retained in adult moths.

Weiss trained caterpillars to avoid the odour of ethyl acetate, a chemical commonly used in nail polish removers. Caterpillars and moths are usually indifferent to the smell of ethyl acetate, but by pairing exposure to the odour with mild electric shocks, the scientists successfully taught these caterpillars to avoid the odour. Notably, the majority of moths choosing air as adults had also made the same choice as caterpillars, suggesting that individual preferences survived metamorphosis.

This study has shed some light on the intricacies of metamorphosis. Scientists have now set aside the notion that a caterpillar is completely disintegrated into a blended soup while in its cocoon. Instead, they now agree that it is more likely that certain parts of the brain may remain intact during the transition.

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Meet the people trying to help. Environment COP26 nears conclusion with mixed signals and frustration. A new generation Complete metamorphosis likely evolved out of incomplete metamorphosis. The oldest fossilized insects developed much like modern ametabolous and hemimetabolous insects—their young looked like adults. Fossils dating to million years ago, however, record the emergence of a different developmental process. Around this time, some insects began to hatch from their eggs not as minuscule adults, but as wormlike critters with plump bodies and many tiny legs.

In Illinois, for example, paleontologists unearthed a young insect that looks like a cross between a caterpillar and a cricket, with long hairs coating its body. It lived in a tropical environment and likely rummaged through leaf litter for food. Biologists have not definitively determined how or why some insects began to hatch in a larval form, but Lynn Riddiford and James Truman , formerly of the University of Washington in Seattle, have constructed one of the most comprehensive theories.

They point out that insects that mature through incomplete metamorphosis pass through a brief stage of life before becoming nymphs—the pro-nymphal stage, in which insects look and behave differently from their true nymphal forms. Some insects transition from pro-nymphs to nymphs while still in the egg; others remain pro-nymphs for anywhere from mere minutes to a few days after hatching. Perhaps this pro-nymphal stage, Riddiford and Truman suggest, evolved into the larval stage of complete metamorphosis.

Perhaps million years ago, through a chance mutation, some pro-nymphs failed to absorb all the yolk in their eggs, leaving a precious resource unused. In response to this unfavorable situation, some pro-nymphs gained a new talent: the ability to actively feed, to slurp up the extra yolk, while still inside the egg.

If such pro-nymphs emerged from their eggs before they reached the nymphal stage, they would have been able to continue feeding themselves in the outside world.

Over the generations, these infant insects may have remained in a protracted pro-nymphal stage for longer and longer periods of time, growing wormier all the while and specializing in diets that differed from those of their adult selves—consuming fruits and leaves, rather than nectar or other smaller insects.

Eventually these prepubescent pro-nymphs became full-fledged larvae that resembled modern caterpillars. In this way, the larval stage of complete metamorphosis corresponds to the pro-nymphal stage of incomplete metamorphosis. The pupal stage arose later as a kind of condensed nymphal phase that catapulted the wriggly larvae into their sexually active winged adult forms.

Some anatomical, hormonal and genetic evidence supports this evolutionary scenario. Anatomically, pro-nymphs have a fair amount in common with the larvas of insects that undergo complete metamorphosis: they both have soft bodies, lack scaly armor and possess immature nervous systems.