Butterflies in Canada pass through the winter in a dormant state referred to as a diapause. The diapause may be spent in any one of their four life stages. It could be as an egg attached to a food plant, as a caterpillar hidden under a piece of bark, as a pupa concealed under a branch or as an adult butterfly. Because of cold temperatures, very few butterflies survive a Canadian winter as adults. Some hibernate, the mourning cloak for one; others migrate to warmer climates: the monarch may be our best-known example.
Although it is precariously late in the season for butterflies to be active, white cabbage butterflies, sulpher-coloured butterflies and many fritillaries (large orange butterflies with white and black spots) still visit flowers late into the fall.
As butterfly caterpillars (larvae) grow they must molt or shed their skin because it will only stretch so far. Caterpillars that hatch from the egg are called first instar (first stage) larvae. They may pass through as many as five instars, each one larger than the previous, until the final molt reveals the pupa case rather than another caterpillar.
Butterfly pupae are exposed to the weather rather than being encased in a cocoon as moths are. To prevent it from becoming food for birds and other animals the chrysalis is coloured to blend with its surroundings, and decorated with barbs to resemble curled-up dead leaves.
The pupa is usually attached by a series of hooks that are locked onto a silken pad left by the caterpillar and supported around the middle by a girdle of fine strands of silk. During this phase the hormone that causes the caterpillar to form a pupa is held in check by the juvenile hormone. When the amount of juvenile hormone decreases, the final molt and pupal stage are allowed to develop. The pupa is said to be the resting stage, yet it is a time of the most complicated of all changes when many of the caterpillar cells begin to break down and another group of cells begins to grow and multiply. It is these new cells, with the help of hormones and their own DNA, that create the adult butterfly.
When all changes have been made and the adult butterfly is ready to emerge, it splits the pupal case at the head end and crawls out. The body of the butterfly is full of fluid that it immediately begins to pump into the small, thick wings. After a few hours in the sun the wings are completely extended and dry and the adult butterfly is ready to seek a mate and renew the lifecycle.
Butterflies are extremely sensitive to changes in habitat and are an early indicator of trouble in the environment.
From a worm to a butterfly is a big and extremely complicated step however, billions of butterflies flawlessly go through this process each year.
Photo by Jim Ferguson
Although it is precariously late in the season for butterflies to be active, white cabbage butterflies, sulpher-coloured butterflies and many fritillaries (large orange butterflies with white and black spots) still visit flowers late into the fall.
As butterfly caterpillars (larvae) grow they must molt or shed their skin because it will only stretch so far. Caterpillars that hatch from the egg are called first instar (first stage) larvae. They may pass through as many as five instars, each one larger than the previous, until the final molt reveals the pupa case rather than another caterpillar.
Butterfly pupae are exposed to the weather rather than being encased in a cocoon as moths are. To prevent it from becoming food for birds and other animals the chrysalis is coloured to blend with its surroundings, and decorated with barbs to resemble curled-up dead leaves.
The pupa is usually attached by a series of hooks that are locked onto a silken pad left by the caterpillar and supported around the middle by a girdle of fine strands of silk. During this phase the hormone that causes the caterpillar to form a pupa is held in check by the juvenile hormone. When the amount of juvenile hormone decreases, the final molt and pupal stage are allowed to develop. The pupa is said to be the resting stage, yet it is a time of the most complicated of all changes when many of the caterpillar cells begin to break down and another group of cells begins to grow and multiply. It is these new cells, with the help of hormones and their own DNA, that create the adult butterfly.
When all changes have been made and the adult butterfly is ready to emerge, it splits the pupal case at the head end and crawls out. The body of the butterfly is full of fluid that it immediately begins to pump into the small, thick wings. After a few hours in the sun the wings are completely extended and dry and the adult butterfly is ready to seek a mate and renew the lifecycle.
Butterflies are extremely sensitive to changes in habitat and are an early indicator of trouble in the environment.
From a worm to a butterfly is a big and extremely complicated step however, billions of butterflies flawlessly go through this process each year.
Photo by Jim Ferguson
No comments:
Post a Comment