The Butterfly

Sep 28, 2008 Features / Columnists, Interesting Creatures in Guyana

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According to some mythical legends, a butterfly is the personification of a person’s soul, whether they be living, dying or are already dead.

Another superstitious belief is that once a butterfly lingers in certain areas, there is a likelihood that someone you love the most will visit.

Some superstitious believers have, however, declared that a large number of butterflies are in fact bad omens.

But according to researchers, butterflies are simply insects of the order Lepidoptera that are notable for their unusual life cycle.

With a larval caterpillar stage, an inactive pupal stage and a spectacular metamorphosis, butterflies are able to transform into a familiar and colourful winged adult form.

It is believed that butterflies have very short life spans. However, in their adult stage, they can live from a week to nearly a year depending on the species.

Many species have long larval life stages while others can remain dormant in their pupal or egg stages and thereby survive for long periods.

Butterflies may have one or more broods per year and the number of generations per year may vary based on the atmosphere of temperate to tropical regions.

Their eggs consist of a hard-ridged outer layer of shell called the chorion, which is lined with a thin coating of wax; this prevents the egg from drying out before the larva has had time to fully develop.

Each egg contains a number of tiny funnel-shaped openings at one end called micropyles; the purpose of these holes is to allow sperm to enter and fertilise the egg.

The eggs are fixed to a leaf with a special glue which hardens rapidly, and as it hardens it contracts, deforming the shape of the egg.

The egg stage lasts at least for about a few weeks in most butterfly species. It has been discovered that butterfly larvae or caterpillars consume plant leaves and spend practically all of their time in search of food.

They mature through a series of stages called instars and near the end of each instar, the larva undergoes a process called apolysis in which the cuticle, a mixture of chitin and specialised proteins, is released from the epidermis.

The epidermis then begins to form a new cuticle beneath. At the end of each instar the larva moults the old cuticle and the new cuticle rapidly hardens and pigments. The development of the butterfly wing pattern begins by the last larval instar.

Wings or wing pads are not visible on the outside of the larva, but when larvae are dissected, tiny developing wing disks can be found on the second and third thoracic segments, in place of the spiracles that are apparent on abdominal segments.

Wing disks develop in association with a trachea that runs along the base of the wing, and are surrounded by a thin peripodial membrane, which is linked to the outer epidermis of the larva by a tiny duct.

Wing disks are very small until the last larval instar, when they increase dramatically in size, are invaded by branching tracheae from the wing base that precede the formation of the wing veins, and begin to develop patterns associated with several landmarks of the wing.

Near pupation, the wings are forced outside the epidermis under pressure from the hemolymph, and although they are initially quite flexible and fragile, by the time the pupa breaks free of the larval cuticle they have adhered tightly to the outer cuticle of the pupa.

Within hours, the wings form a cuticle are so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings.

The pupal transformation into a butterfly through metamorphosis has held great appeal to mankind. To transform from the miniature wings visible on the outside of the pupa into large structures usable for flight, the pupal wings undergo rapid mitosis and absorb a great deal of nutrients.

If one wing is surgically removed early on, the other three will grow to a larger size. In the pupa, the wing forms a structure that becomes compressed from top to bottom and pleated from proximal to distal ends as it grows, so that it can rapidly be unfolded to its full adult size.

Several boundaries seen in the adult colour pattern are marked by changes in the expression of particular transcription factors in the early pupa.

Most species of butterflies are day-flying so they regularly attract attention. In fact their diverse patterns formed by their brightly coloured wings and their erratic yet graceful flight have made butterfly watching a fairly popular hobby to many humans.

Some are known to migrate over large distances and have even evolved symbiotic and parasitic relationships with social insects such as ants.

It is said too that they are very important economically as one of the major agents of pollination.
However, a number of species are regarded as pests because they are known to cause damage to domestic crops and trees.

They feed primarily on nectar from flowers and some also derive nourishment from pollen, tree sap, rotting fruit, dung, and dissolved minerals in wet sand or dirt.

Adult butterflies, however, consume only liquids and these are sucked by means of their proboscis. They feed on nectar from flowers and also sip water from damp patches.

This they do for water, for energy from sugars in nectar and for sodium and other minerals which are vital for their reproduction.

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