BUTTERFLIES; THE WINGED BEAUTY
BY- Mr. RAJESH KUMAR MOHAPATRA
Butterflies are the scaly winged insects with clubbed antennae. They belong to the Phylum, Arthropoda; Class, Insectaand Order, Lepidoptera. There are 1,50,000 species of butterflies and moths belonging to the Order Lepidoptera from which 1,78,20 are butterflies. There are 1501 identified species of butterflies found in India. Order Lepidoptera (Gr. lepis, scale; pteron, wing) have been classified in to two sub-Orders: Rhopalocera(Gr. rhopalon, club; keras, horn) including butterflies and Heterocera(Gr. heteros, other; keras, horn) including moths. Rhopalocera is further divided in to five families: 1. Hasperiidae, 2. Papilionidae, 3. Pieridae, 4. Lycaenidae and 5. Nymphalidae.
Diversity: India has been divided in to 10 Biogeographical zones. All the zones have butterfly diversity but it virtually depends on the presence of host plants and climatic condition of that region. Sikkim, the organic state of India has about 50% butterfly species diversity of the India. There are 321 species of Hasperiids, 107 species of Papilionids, 109 species of Peirids, 443 species of Lycaenids and 521 species of Nymphalids in India. Southern bird wing (Triodes minos) and Grass jewel (Chilades trochylos) are the largest and smallest butterflies of India, respectively.
Life cycle: Life cycle of butterflies include four stages (egg, larva or caterpillar, pupa or chrysalis, imago or adult) with a complete and complex metamorphosis. Butterflies are dioecious. Fertilization is internal. Eggs are laid on the upper surface of the host plant leaf immediately or after 1-2 days of fertilization. Egg is covered by a thin pellicle which is variedly sculptured and has a rosette of cells on its extreme summit. This cell rosettehas a microscopic pore called Micropyle in its centre used for fertilization by sperm and also for respiration of the developing embryo. Larva or caterpillar hatches out after about 3 or 4 days depending on the surrounding temperature. Caterpillar is 14 segmented. Head is scleritized and is immediately followed by three thoracic segments each having a pair of true leg ending in a horny claw. From the 10 abdominal segments, prolegs are present from third to sixth abdominal segment and in the last abdominal segment. Spiracles, the breathing pores are present on the plural region through which air enters certain tubes ramifying within for the aeration of the blood. It is present in 1st thoracic, then 1st abdominal to 8th abdominal segment. The skin of the caterpillar split at the middle of the back and the larva crawl out of it. This is called moulting. The stage between the moulting is called as Instar. There are five Instars in most of the species. Last Instar is called as Prepupa. Pupa is the stage of resting and differentiation, resulting in all the organs outlined. However its wings are small and applied close to the thorax on the lower side and the proboscis is straightened to lie between the wing case. Just before emergence, the pupal case splits open on the back. The butterfly crawls out of the chrysalis and find a suitable perch. Initially the wings are wrinkled and shriveled but slowly blood is pumped in to the veins. At this time the butterfly is very vulnerable to attacks from predators. Then the butterfly becomes ready to fly in search of food and mate. Adult butterfly can only feed the liquid food by its sucking type of mouth part.
Colouration: Colouration in butterfly is determined by two colour systems i.e., Structural colour system which relies on the reflection, refraction and interference of light by scales on the wing of the butterflies and Chemical colour system which relies on the pigments present on their body and wing such as melanin, carotinoids and pterin (only found in Pierids).
Mimicry and camouflage: Some butterflies exhibit mimicry and camouflage for self-protection. Mimicry is the protective imitation in appearance and behaviour of one species to the other. Mimicry is of two types; Mullerian mimicry (proposed by Fritz Muller) and Batesian mimicry (proposed by H.W. Bates). In Mullerian mimicry unpalatable species mimic with each other by the convergence of wing pattern. The butterflies become unpalatable by feeding the host plant leaves which synthesizes alkaloids, tannins, cardiac glycosides for defense against browsing. These chemicals are retained in the adults and render them unpalatable to predators. In terms of predation pressure the individuals of all the Mullerian species act as a single species and the predator that eats an individual of any of the Mullerian species does not eat any individuals of any other species. Common rose (Pachliopta aristolochiae) showsMullerian mimicry to Crimson rose (Pachliopta hector). In Batesian mimicry the palatable butterfly species mimic to the unpalatable (module) butterfly species for their protection. Danaid eggfly(Hypolimnas misippus) male and Danaid eggfly female show Batesian mimicry to Great eggfly (Hypolimnas boline) male and Plain tiger (Danaus chrysippus) female, respectively. Camouflage is the protective resemblances with the inanimate objects of surrounding. Pupa of Mime (Papilio clytia) butterfly camouflage as a dried broken twig of host plant.
Importance: Butterflies are valuable pollinators. Pollination by butterfly is called as Psycophily(Gr. psyche, butterfly; philos, friend). Butterflies are one of the important food chain components for the birds, reptiles, spiders and predatory insects like Preying-mentis. They are good indicators of environment as they are sensitive to change in the environment e.g. decrease in the number of host plant or nectar plant. They are also good candidate material for the study of genetics, insect-plant interaction and co-evolution.
Threats: Butterflies are the crucial part of our environment. But now they are under potential threats due to the following reasons. Fragmentation and degeneration of habitat by forest fire, cattle grazing in protected area, vast monoculture of some economic important plants and tea plantation. Non implementation of law which includes illegal trading of butterflies especially the Papilionids creating major threat for them. Threats also include the general ignorance like the application of pesticides and lack of awareness about the butterfly and its habitat. If they are not protected timely, the day is not far when we will lose these lovely species to obscurity.
Conservation: Butterflies can be conserved by controlling forest fire and cattle grazing in protected areas by forest department, participation of local people in constituting butterfly parks, research stations and butterfly farming, popularizing butterfly eco-tourism, establishment of Wildlife Sanctuaries exclusively for endangered butterfly species and creating awareness in common people. To promote the butterfly ecotourism the first Butterfly Park of India was established at Bannerghat National Park, Bangalore; inaugurated in November 25, 2006. The second butterfly park of India was established at Shimla, Himachal Pradesh. The first Open-air Butterfly Park was established at Rangrang, Sikkim. There are 450 species of butterflies have been protected under The Wildlife (Protection) Act, 1972; from which 128 species under Schedule-I, 303 species under Schedule- II and 19 species under Schedules- IV. Growth of small patches of vegetation (larval host plants and nectar plants) can provide home for these threatened butterflies.
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