Tuesday, February 24, 2009

New species of spiders in Ranchi city.

Colourful spiders of Ranchi city.
Dr. Nitish Priyadarshi

Changes in temperature and mild winters have allowed the new species of spider to reproduce and invade gardens across Ranchi city of Jharkhand State of India. Called the "False Widow" its bite does not kill, but does cause intense pain and severe swelling. In other words, if you hate spiders, you have another reason to fear global warming.
Species have started turning up in the gardens and houses. This year peculiar thing is that different varities and colourful spiders are being seen in the backyards. Most of them seems to be migrated from other part of the country to this city or from other country like Europe and America.
Earlier we use to see only one or two types of spiders especially small and black. But from last few years spiders of different size and colours are seen. Though their numbers may be few but due to their exotic colours they are attracting people. Most interesting is the construction of the Silver Webs in the spiral form.
The pictures above very much resembles to Silver argiope (Argiope argentata) This spectacular orb-weaving spider is common in Southern California in the Fall, especially on prickly-pear plants. They are also found in Arizona, Central and South America as well as South Florida. The male is much smaller than the female. The spider includes zig-zag structures called stabilimenta in the orb web, probably in order to make it more visible to birds who might otherwise fly into it accidentally and destroy it. These critters can bite and leave a slight sting and itch on the victim, though they are not particularly dangerous.

From last several years like Parthenium grass, new species of the insects, frogs and even mosquitoes have been recognised in Ranchi city. Thanks to climate change, pollution and global warming.

The significance of insects in ecology needs no emphasis. Spiders also have a very significant role to play in the ecology by being exclusively predatory (Wise, 1993) and thereby regulate insect populations. All spiders are venomous but only a few species are venomous enough to harm humans. However, the venom of some spiders is useful in study of neuromuscular and cardiac pharmacology. It is likely that spider silk will be the material of the future as its silk is the toughest material known.
Spiders are ancient animals with a history going back many millions of years. They have always been with us, an ancient source of fear and fascination. They are abundant and widespread and are natural controllers of insect populations. Wherever you live, you're always close to a spider.

Spiders were among the earliest animals to live on land. Despite this their fossil record is relatively poor. They probably evolved about 400 million years ago from thick-waisted arachnid ancestors that were not long emerged from life in water. The first definite spiders, thin-waisted arachnids with abdominal segmentation and silk producing spinnerets, are known from fossils like Attercopus fimbriungus. This spider lived 380 million years ago during the Devonian Period, more than 150 million years before the dinosaurs.
By the Jurassic Period (191 - 136 million years ago), when dinosaurs roamed the earth, the sophisticated aerial webs of the orb weaving spiders had developed to trap the rapidly diversifying hordes of flying insects.

Wise D H 1993 Spiders in Ecological Webs, Cambridge Univ. Press, London 342 pp

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