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Perhaps only a balerine dance can be so graceful as a butterfly flying. While a dance balerine means much work, sacrifices and passion, the graceful flight of the butterfly IS the naturalness, the delicacy and the uniqueness that only God can inspire. Let’s enjoy these delicate wonders.
A butterfly is an insect of the order Lepidoptera. Like all Lepidoptera, butterflies are notable for their unusual life cycle with a larval caterpillar stage, an inactive pupal stage, and a spectacular metamorphosis into a familiar and colourful winged adult form.
The egg: Butterfly eggs consist of a hard-ridged outer layer of shell, called the chorion. This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully develop. Butterfly eggs are fixed to a leaf with a special glue which hardens rapidly. As it hardens it contracts, deforming the shape of the egg. This glue is easily seen surrounding the base of every egg forming a meniscus. The nature of the glue is unknown and is a suitable subject for research. The same glue is produced by a pupa to secure the setae of the cremaster.
The egg stage lasts a few weeks in most butterflies but eggs laid close to winter, especially in temperate regions, go through a diapause stage, and the hatching may take place only in spring.
The Caterpillar: Larvae, or caterpillars, are multi-legged eating machines. They consume plant leaves and spend practically all of their time in search of food. Caterpillars mature through a series of stages, called instars. Near the end of each instar, the larva undergoes a process called apolysis, in which the cuticle, a mixture of chitin and specialized proteins, is released from the epidermis and the epidermis 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. Development of butterfly wing patterns begins by the last larval instar.
Some caterpillars have the ability to inflate parts of their head to appear snake-like. Many have false eye-spots to enhance this effect. Some caterpillars have special structures called osmeteria which are everted to produce smelly chemicals. These are used in defense.
Host plants often have toxic substances in them and caterpillars are able to sequester these substances and retain them into the adult stage. This helps making them unpalatable to birds and other predators. Such unpalatibility is advertised using bright red, orange, black or white warning colours.
Wing development: 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 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 (in obtect pupae). Within hours, the wings form a cuticle so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings.
Pupa: When the larva is fully grown, hormones are produced. At this point the larva stops feeding and begins “wandering” in the quest of a suitable pupation site, often the underside of a leaf. The larva transforms into a pupa (or chrysalis) by anchoring itself to a substrate and moulting for the last time. The chrysalis is usually incapable of movement, although some species can rapidly move the abdominal segments or produce sounds to scare potential predators.
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 color pattern are marked by changes in the expression of particular transcription factors in the early pupa.
Adult or imago: The adult, sexually mature, stage of the insect is known as the imago. As Lepidoptera, butterflies have four wings that are covered with tiny scales. The fore and hindwings are not hooked together, permitting a more graceful flight. An adult butterfly has six legs, but in the nymphalids, the first pair is reduced. After it emerges from its pupal stage, a butterfly cannot fly until the wings are unfolded. A newly-emerged butterfly needs to spend some time inflating its wings with blood and letting them dry, during which time it is extremely vulnerable to predators.
Butterflies comprise the true butterflies (superfamily Papilionoidea), the skippers (Superfamily Hesperioidea) and the moth-butterflies (Superfamily Hedyloidea). Butterflies exhibit polymorphism, mimicry and aposematism. Some are known to migrate over large distances. Some butterflies have evolved symbiotic and parasitic relationships with social insects such as ants. Butterflies are important economically as one of the major agents of pollination. In addition, a number of species are pests, because they can damage domestic crops and trees.
Most species are day-flying so they regularly attract attention. The diverse patterns formed by their brightly coloured wings and their erratic yet graceful flight have made butterfly watching a fairly popular hobby.
Butterflies are today distributed throughout the world except in the very cold and arid regions. There are an estimated 17,500 species of butterflies (Papilionoidea) out of about 180,000 species of Lepidoptera.
Presently butterflies are classified in three superfamilies, Hedyloidea, consisting of the ‘American moth-butterflies’, Hesperioidea, consisting of the ’skippers’ and Papilionoidea or ‘true butterflies’. The last two superfamilies are probably sister taxa, so the butterflies collectively are thought to constitute a natural group or clade.
The scope of the term butterfly depends on how far the concept is extended. Currently, most experts include the superfamilies Hedyloidea (the American moth-butterflies), Hesperioidea (the skippers) and Papilionoidea (the so-called ‘true’ butterflies). This concept of butterflies including the Hedyloidea is a recently expanded one, but it makes the group a natural clade, the Rhopalocera.
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