After the butterfly lays its eggs, they enter their larva stage – an astounding stage marked by voracious eating and rapid development. Caterpillars periodically shed their exoskeleton (old skin) as they increase in size.
A caterpillar then creates a hard shell known as a chrysalis that hangs motionlessly from its body. From the outside, however, nothing appears to happen inside; but inside there’s an extraordinary transformation taking place!
Egg
Butterflies go through four distinct life stages: egg, larva, pupa and adult. Each stage plays an essential part in their development – beginning with egg stage but going beyond this point as well. It is remarkable to witness what goes on before an egg even hatches!
Female butterflies lay their eggs on specific plants known as host plants, providing the nourishment for an egg to develop into an adult butterfly. Once fertilized by male sperm, however, this egg becomes a caterpillar and enters its second stage of butterfly lifecycle: becoming an adult butterfly.
The caterpillar’s digestive process to become an adult butterfly is an exhausting one; as its energy reserves become depleted quickly. To gain weight and size quickly, caterpillars feed on host plants as well as any food sources they find nearby in order to gain weight quickly – this process may last anywhere between several days to several weeks, depending on species.
Once a caterpillar reaches its final growth stage, it stops eating and searches for an appropriate place to metamorphose into an adult butterfly. Once it finds an ideal location, it forms what’s known as a pupal skin or chrysalis. This protective covering may be suspended from a branch or leaf canopy or even be hidden underground depending on the species of butterfly it belongs to – with some lasting several weeks up to several months or even years depending on species and its species of choice.
Once the chrysalis is ready, it begins an incredible transformation – shedding its skin and breaking apart to take form as an adult butterfly! This process is so demanding on caterpillars they may lose as much as 50% of their weight while in pupal stage!
As soon as a butterfly emerges from its chrysalis, it must immediately search for a mate – often only taking days or even hours. Once one is found, mating occurs followed by egg laying; thus continuing the cycle.
Caterpillar
As soon as caterpillars hatch from eggs, they begin eating and rapidly expanding – often reaching 100 times their original size by the time they reach larval stage. Unfortunately, caterpillars face harsh weather conditions, disease, parasites, predators, parasites and predators which make this stage extremely hazardous; only a minority of eggs that hatch into caterpillars make it through.
As soon as a caterpillar becomes too big for its current skin, it molts (shedding or molting). This process occurs four to six times during its growth period; each time is called an instar. As it sheds more and more skin from time to time until its body can no longer stretch its previous layer and sheds again; during this stage it may writhe or squirm for several hours as its new soft, wet covering expands into place.
Once the caterpillar reaches its final instar, it seeks out a safe place to become an adult butterfly or moth. After finding some suitable foliage such as leaf litter or log pile, it forms its chrysalis. This protective case acts like an incubator while it goes through tremendous internal changes; digestive juices break down its old body tissues into “tissue cell soup”, which then forms into new body parts for its winged lifecycle.
The caterpillar also creates wings from another membrane called an elytra, similar to its exoskeleton but more flexible; this provides butterflies with wings to fly. Attaching itself securely to its host chrysalis via silk threads.
After an extended transformation period that can last anywhere from several days to an entire year, a caterpillar will emerge from its chrysalis as an adult butterfly or moth with wings that appear damp and wrinkled at first – however they soon fill with fluid so they dry and become strong enough for flight!
Pupa
Once a caterpillar has transformed itself into a chrysalis, its time for transformation to come is complete. Pupae may take from days to years depending on temperature; during that period of time their mummy-like skin continues to develop wings, legs, reproductive organs and more!
At its pupal stage, you can clearly witness how a butterfly transforms into an adult insect. Its colors and markings become more vibrant; its black bands appear wider and velvetier; its first pair of legs move closer to its head; white spots on prolegs become less evident compared to instars 3, 4 or 5, and female butterflies may reveal their genitalia at this time.
At this stage, an insect also releases digestive juices to break down most of its tissues, creating what is known as “tissue cell soup”. From this “soup”, new wings, eyes, legs, mouthparts, an expanded abdomen are developed. Moth caterpillars spin silken cocoons while butterflies form chrysalises that provide protection against predators and the elements as their metamorphosis takes place.
Scientists have long hypothesized that the holometabolous pupal stage evolved as an enhanced version of an ancestral stage that underwent incomplete metamorphosis, or hemimetaboly. Support for this theory comes from its parallelism between Kr-h1 expression in last-instar hemimetabolous larvae and their respective pupae; recent discoveries on molecular signalling that regulate metamorphosis; Br-C expression which was once suppressed by juvenile hormone (JH), but which was lifted at end-instar larvae were required for initiating pupal skin formation [54] .
As it prepares to emerge as an adult, the caterpillar/butterfly breaks open its pupal case and emerges, climbing out. Once out of its cocoon it hangs upside-down for up to two hours so its wings may expand fully; after which it is ready for flight.
Adult
At the final stage of a butterfly’s lifecycle is its adult stage: emerging from their chrysalises to find a mate and lay eggs. Female butterflies play an especially vital role in this stage by producing pheromones that attract males.
Once a caterpillar reaches maximum development and has completed all its moults, it is ready to transform into an adult butterfly. When this stage arrives, they find a safe location where they form their chrysalis, an external covering made up of chitin and proteins which acts like an umbrella to shield the caterpillar from predators while still looking attractive to their surroundings. Often brightly-coloured chrysalises help camouflage them within their environment while protecting from potential danger.
Inside its chrysalis, caterpillars experience an extraordinary transformation called metamorphosis. Cell by cell, all its old body parts are broken down and rebuilt as butterfly parts; this process may take from days to several months.
Once a chrysalis has formed into its new body, it breaks down and dissolves its exoskeleton to reveal an adult insect under. This process, called ecdysis, occurs due to an enzyme present in butterfly’s blood called chymotrypsin. Once this has taken place, the butterfly spends several hours or days hanging upside down from its chrysalis until its wings can fully expand under air movement around it.
At this stage, an adult butterfly is known as an imago. Once it has released pheromones to attract males for several days or weeks, it is ready for mating. After mating, females will search for an appropriate plant where to lay their eggs based on leaf colour and shape; beating on leaves surface may release specific chemicals known as “plant odour”, helping identify their desired egg-laying site.
Discover the world of the butterfly with Twinkl’s interactive book The Cautious Caterpillar. This engaging tale teaches children the value of courage and not being afraid to change, making it suitable for whole-class storytelling sessions.