Good news for Delhi's ecological balance as Yamuna biodiversity park witnessed good number of dragonflies and damselflies. Incidentally, dragonflies along with damselflies are among the most significant organisms in the wetland ecosystems that are under threat. In biological terms, they are called Odonates.
According to Dr Faiyaz Khudsar, environmentalist and ecologist, these flies belong to the order Odonata, which is a primitive group of insects, and have first appeared in the carboniferous age about 220 million years ago and have the unique distinction of undertaking the first flight by any living creature on this earth. However the modern dragonflies' species that we often see today have evolved in the Mesozoic era along with the dinosaurs around 150 million years ago,” Said Dr Faiyaz.
Importantly, today, in the whole world, a total of 5329 species are known, and these species are classified into 619 genera and 33 families.
It is pertinent to mention here that about 500 species are known from India in which 49 were recorded from Delhi in 1996 by Zoological Survey of India.Dr Faiyaz Khudsar further said that conserving functional wetland ecosystems are not only important for addressing recharge of subsoil and deep aquifer but become home for dragonflies and damselflies protecting us form malaria and dengue.
Their larvae, called 'naiads', are voracious feeders of mosquito larvae, particularly in stagnant water bodies. Adult also feed on mosquitoes, blackflies and other blood sucking flies. Their larval stage may last as long as five years. When the larva is ready to metamorphose into an adult, it climbs up a reed or other emergent plant like Typha and Phragmytis. Exposure to air causes the larvae to begin breathing. The skin splits at a weak spot behind the head and the adult dragonfly crawls out of its old larval skin. The adult stage of larger species of dragonfly can last as long as four months.Elaborating more about Dragonflies, Dr Fiyaz, said that their role as top predator for other insects particularly mosquitoes and flies gives them direct utility to public health. “Their utility becomes stronger in a city like Delhi, which regularly faces epidemics of mosquito borne diseases,” he added.
They are aquatic insects and their life history is fully dependent on freshwater bodies like rivers and ponds. Female dragonfly lay eggs in or near water, often on floating or emergent plants.
At the time of laying eggs, some species will submerge themselves completely in order to lay their eggs on a good surface. Most of the dragonfly's life is spent in the larval stage beneath the water's surface and they feed on all types of mosquito larvae.
In the urban areas of Thailand, larvae of the container-breeding dragonfly, Granite Ghost (Bradinopyga geminata) was successfully used to control Aedes mosquito, an important vector of the dengue fever.
DDA Biodiversity Parks is an important green infrastructure of Delhi.The initiative to count dragonflies and damselfly species of Delhi is being undertaken this year by BNHS New Delhi. A team of experts and students headed by Mohammad Faisal, Entomologist surveyed wetlands of Yamuna Biodiversity Park on Saturday.