Butterfly Metamorphosis-How It Works

Butterfly Life Cycle What causes the radical transformation from caterpillar to butterfly? How does a caterpillar rearrange itself into a butterfly? What happens inside a chrysalis or cocoon?

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cel l growth and differentiation.

In insects growth and metamorphosis are controlled by hormones synthesized by endocrine glands near the front of the body. Neurosecretory cells in an insect's brain secrete a hormone that activates glands, which secrete a second hormone to produce juvenile hormone, which prevents the development of adult characteristics during the shedding of the outer cuticle (skin).

Egg

Monarch Butterfly Eggs The butterfly egg is spherical or ovate shaped, varying in color and size. It is covered by chorion, a hard shell that protects the egg, and is lined with a waxy layer that prevents dehydration. It is full of nutrients and is commonly the first meal for the newly hatched larva. There is a small opening called a micropyle which allows sperm to enter the egg for fertilization while inside the female.

To protect the egg and embryo that is forming, the eggs are attached to a leaf by the butterfly using an adhesive-like substance that glues the egg to the plant leaf. The nature of the “glue” is still fairly unknown in the scientific community. For protection, the eggs are often laid on the underneath side of the leaf so as not to be visible to predators. It is essential for the eggs to be laid on the host plant for that particular butterfly species. Eggs are sometimes laid in groups, although many butterflies such as the Monarch lay their eggs singly. The average time for the embryo to develop is 7-14 days but in instances where the egg is the overwintering stage, the embryo may take months to develop.

Caterpillar (Larvae)

To protect the egg and embryo that is forming, the eggs are attached to a leaf by the butterfly using an adhesive-like substance that glues the egg to the plant leaf. The nature of the “glue” is still fairly unknown in the scientific community. For protection, the eggs are often laid on the underneath side of the leaf so as not to be visible to predators. It is essential for the eggs to be laid on the host plant for that particular butterfly species. Eggs are sometimes laid in groups, although many butterflies such as the Monarch lay their eggs singly. The average time for the embryo to develop is 7-14 days but in instances where the egg is the overwintering stage, the embryo may take months to develop.

American Lady Caterpillar A caterpillar grows really fast. This is because they eat a lot. A caterpillar is really small when it is born. It starts to grow fast. This is because it eats all the time. When a butterfly or moth larva (also known as a caterpillar) first hatches from its egg, it is very small! This young caterpillar is referred to as a First Instar caterpillar

Caterpillars (and all insects) face a challenge as they grow! Unfortunately, their skin cannot grow with them! In order for a caterpillar to grow larger than the skin it had when it hatched, it must make a new, larger skin! The caterpillar does this by first growing a new skin underneath the outer skin. Then, when it is ready, it "sheds" the old skin, and the newer, larger skin underneath is exposed. This process is properly called Molting. After the caterpillar has molted for the first time, it is referred to as a Second Instar and it has some room to grow.

The third instar caterpillar also eats and grows until it is too big for its skin. It molts again, and the caterpillar with its new skin is referred to as a Fourth Instar caterpillar. Most butterflies have 5-6 instars.

Chrysalis (Pupae)

Chrysalis of Gulf Fruitillary Butterfly The pupa,though sedentary, is a stage of great internal turmal and transformation. Nearly all of the larval tissues and organs (eyes, mouth parts, legs, glands, muscles) will be digested and reorganized into the doby of the adult butterfly. Prior to pupation, teh larva loses much of its patterning and its lenght decreases. In addition, the gut is evacuated.

The pupa stage of the butterfly’s life cycle is a time for complete change. The pupa is also known as a chrysalis and is a vessel in which the slow moving caterpillar changes into a winged butterfly. The process begins with the prothoracicotropic hormone (PTTH) triggering the caterpillar to quit eating and start wandering to a place to pupate, which is usually on twigs or other safe areas around their host plants but not necessarily on the host plants. Some butterfly species that over winter as a chrysalis may pupate in the leaf litter close to the ground.

Black Swallowtail Pupa (chrysalis)The chrysalis is immobile so it is important that it be camouflaged into the environment. For example, the Spicebush Swallowtail’s chrysalis takes on a brown or green color depending on the color of the environment. Many chrysalides are leaf shaped and vary in color from yellow, brown, green to silver and gold. Some chrysalides have the ability to wiggle and make a hissing sound in order to frighten predators.

This 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 mouth parts of the caterpillar are transformed into the sucking mouth parts of the butterfly.

Adult

Henry's Elfin Butterfly Aduts emerge from the pupa with short wings that must be expanded with hemolymh. Newly emerged adults, especially those with large, heavy wings, must be able to hang from a twig or other object to successfully enlarge their wings.

The transformation from a hardly recognizable creature to a flight-ready adjut is rapid, occurring over a span of only 20-60 minutes. It is one of nature's most captivating and awe-nspiring phenomona. Sme species cycle through an entire generation in as few as 4-5 weeks with the Monarch butterfly being a familiar example.

Near the end of each stage, the larva undergoes a process called apolysis, mediated by the release of a series of hormones. During this phase, the cuticle, a tough outer layer made of a mixture of chitin and specialized proteins, is released from the softer epidermis beneath, and the epidermis begins to form a new cuticle. At the end of each instar, the larva moults, the old cuticle splits and the new cuticle expands, rapidly hardening and developing pigment.

Development of butterfly wing patterns begins by the last larval instar. Internally, most of the body cavity is taken up by the gut, but there may also be large silk glands, and special glands which secrete distasteful or toxic substances. The developing wings are present in later stage instars and the gonads start development in the egg stage

Butterflies spin the the button of silk to which the chrysalis will attach. Most butterflies have 5-6 instars.