Giant butterflies on way to extinction
Butterflies are natural biotic key to biodiversity conservation as well as conservation of any bio-resource in nature. Species 'assemblage and species' richness in any ecosystem, specially in the forest ecosystem, are significantly preserved by the 'dynamism utilization' of butterfly-plant interaction in natural condition. This trophic dynamism happens in nature when the wild state of the butterfly-plant interaction is not disturbed externally, specially by the humans.
Butterflies are not only very beautiful but also very sophisticated and eclectic creatures. They are highly specific in respective plants selection for trophic relations. They are in strong interaction host plants, nectar plants and shade plants. Assemblage of the three types of plants and natural butterfly multiplication is the process of butterfly-colonization and butterfly-survival. This process has been seriously affected in Bangladesh. The rate of deforestation and reduction of essential plant species on which the butterflies depend stands dangerous. In our forest areas all butterflies are threatened because of their host plant reduction. But the largest butterflies (two species known as birdwings) are serious victims of the situation. They are going to be extinct very soon if necessary measures are not taken immediately.
Butterfly-plant relations and butterfly-survival
As I have said, butterflies are very eclectic for selection of their host plants. This establishes a bonding for maintenance and sustenance of life cycle in butterflies with phenology of host plants. After 3-4 days of emergence, the female giant butterfly becomes ready for laying eggs. As she cannot lay eggs on any plant in her vicinity, she becomes just mad to find her host plant on which egg laying could be done. The ethological behaviour at this movement is very remarkable. The area where females find host plant make there territory. Attracting of male butterflies happens there and then mating occurs. This happens to be the first step of colonizing process.
An adult butterfly visits many flowers, but takes nectar from few selected plants. Most interesting fact is that, a female butterfly lays eggs on plants belonging to a certain family on which the larval development can take place. It means that the female adult does not lay eggs on plants or plant which cannot provide food for the larvae.
It is to be noted that the existence, multiplication and abundance of host plants and other related plants depend on the available activities and functioning of the butterflies; and on the other hand, maintenance and survival of butterfly population depend on the availability and abundance of host plants in the wild state. The reciprocal activities between the butterflies and their host plants cause gene-flow-functioning for floral and faunal species richness. How this species richness happens? Butterfly needs three types of plant population for its life sustainability and population multiplication. First, is host plant that is required for larval growth and adult production; second, is the nectar plant that is needed for the supply of nectar as food for adult activities and sustenance; and third is the shade plant, that is required for taking shelter in the driest day when it is too hot or in the wet days when it rains. The assemblage of three types of plants are needed absolutely without interference of human beings. In connection with that, the maintenance of humidity and other biotic factors interacting together becomes prerequisite for keeping butterfly population in a place at its general equilibrium position (GEP). Then harvest from butterfly population could be made.
If maintenance of this assemblage is hampered, specially in the wild state, then the sophisticated animal butterfly cannot survive there. So, destruction and non-availability of host plants, the nectar and shade plants causes the extinction of the butterfly species. And once a butterfly species becomes extinct; deforestation starts at the molecular level. Consequently forest starts loosing its status, ultimately after few years forest gets poor and poorer in its existence.
The largest butterfly
Birdwing butterflies are the largest butterflies in the world. They belong to the order Lepidoptera and family Papilionidae. The family Papilionidae contains about 700 species distributed throughout the world. They are generally powerful fliers and are among the most conspicuous in the countries where they found. This family includes some of the most splendid of all butterflies. Particularly outstanding are the enormous birdwing butterflies (Ornithoptera spp.), found principally in the Australian region. Females of some of the Ornithoptera spp. have a wing-span of 25cm or more. The males, although smaller, are often arrayed in dazzling gold or green.
In Bangladesh Ornithoptera is not available, but we have two species of birdwings in very restricted areas of forests at present. These are Troides aeacus and Triodes helena. They were distributed all over the forest areas of Bangladesh. The population of the birdwings was large and noticeable. At present their distribution is absent almost in all the forest areas of Bangladesh because of tremendous reduction of their host plants. In connection with this, the birdwings are seriously disturbed in their life style by the humans in the wild state. These butterflies are not only beautiful creatures but also very touchy and sophisticated animals.
In Troides helena, wingspan varies from 15 cm to 19 cm (Bangladesh variety). Fore wing is black, hind wing yellow with black markings, including marginal spots along the hind wing margin, but no internal black dusting on the inner edges of these spots. Male has an additional black submarginal spot in space two and conjoined with marginal spot. The female differs from the male in having another complete series of submarginal black spots and not conjoined with marginal spots.
In Troides aeacus, wingspan varies from 14 cm to 18 cm (Bangladesh variety) and more. T. aeacus is similar to T. helena but hind wing has black dusting on the inner edges of marginal spots in space 2, 3 sometimes in space 4, especially in male. In addition, the female differs with pale streaks in the outer part of the fore wing cell.
Research findings
Researchers of EBBL (Department of Zoology, D.U.) have been working since 1998 on the subject of searching host plants of butterflies in the forests of Bangladesh. They have successfully found the host plants of birdwings in very restricted forest areas. This plant is one kind of climbing vine and uses larger trees to survive. The plant also requires some hedge-supports among the tree populations as underground vegetation. Distribution of the host plant has been tremendously reduced. Only a few plants are found in the region of Sylhet, Chawtali and Lawasora forest areas. In the forest areas of Fashiakhali, Eid Gaon and Eid Ghar of Cox's Bazar district very small population of the plant is still surviving. Researchers of the EBBL have found them after searching for long ten years.
So, the distribution of the birdwing has been confined to extremely restricted areas in our country. As the host plants are surviving under extreme hardship and at the serious risk-stage of extinction, the birdwing will also be extinct very soon in the wild. It is to be noted that, in the forests of Modhupur, Mymemsingh and Bhawal National Park the birdwings are no more available.
The researchers have found some vital key factors for colonizing the birdwing butterflies by establishing the population sustenance of host plant and the assemblage of its supporting plants in the forests. The colonization of the nectar plants and shade plants together with host plants provides good status of a forest ideal for survival of birdwings. Extinction of the vine host plants for the largest butterflies must be sopped by us without any delay, otherwise there no way will be left to protect the giant butterflies, (natural wealth of the country and the forest).
Suggestions
For the necessary action to protect the largest butterflies and to utilize their role in the economic, environmental, conservational and ecotouristic welfare the following may adopted. Immediate adoption of the some may land us in the state to even protect the forest ecosystem as a whole.
- Necessary mechanization for augmentation of the species richness and species assemblage of both flora and fauna should be taken into consideration scientifically on immediate basis.
- “Birdwings-plant dynamism” should be made practicable scientifically in the forest areas immediately in the countries where still the trace of birdwings' 'natural availability' is noticed.. This will make the forest status sustainable in the practicable areas very quickly.
- Butterfly-colonization mechanism (scientific process) should be immediately established in the forest areas which will make it easy to prepare the butterfly park for ecotouristic and economic advancement.
- Butterfly-plant association and dynamism should be made practical in the interest of augmentation of the ecotourism industry in the forest areas.
- Ecotourism industry must be made bio-resource oriented, local people participatory and endemic flora-fauna enriched.
- Forest officials should be very friendly and helpful in welcoming the real researchers with providing possible logistics and spaces.
- Collaborative efforts are necessary both from the part of scientists and forest administration for making the research environment more practical and effective.
- Finding out arrays of utilizing butterfly resources as the key tools for economic, environmental, conservational and ecotouristic welfare and effectiveness.
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