7.4 Spiders

Colourful web-weavers-and scary to some-spiders are little known or appreciated creatures. Like insects, they are invertebrates (they have no backbone). But they are not insects; rather, they are arachnids, related to scorpions, ticks, mites and king crabs.

There are 30,000 species of spiders distributed over 60 families worldwide. In India there are about 43 families of spiders.

Spiders inhabit a wide range of ecosystems because they can tide over periods of food shortage and take advantage of periods of abundance. In the Western Ghats, they are found in a variety of microhabitats-tree bark and trunks, rock crevices, under leaves and stones, below bushes, on walls of houses, in tunnels and burrows, and near water.

Spiders as big-control agents

Spiders are important biological control agents of animal and plant pests. The giant crab spider (Heteropoda venatoria) prefers cockroaches and other insects. Wolf spiders relish brown planthoppers-a pest dreaded by rice farmers.

Threats to spiders

· Many pesticides kill beneficial spiders as well as insect pests. Indiscriminate use can lead to increases in pest numbers because spiders and other predators are wiped out. Some species of spider may be endangered because of such use.

· As with all species, the destruction of habitat through deforestation and other changes may reduce the number of spiders.

· Many people are afraid of spiders. Instead of being seen as friends and vital parts of the ecosystem, spiders are often indiscriminately killed.

Conservation approaches

· Raise the general awareness of the important role spiders play in the Western Ghat ecosystem.
· Study spiders' role as big-control agents in agriculture.
· Explore various uses of silk-for instance, for fishing nets. The use of webs in bulletproof vests is being studied.
· Do not destroy forest patches-the home of many spiders.
· Study the role of spiders in maintaining the stability of an ecosystem and their relation to other forms of life.

Arachnids vs insects

Arachnids vs insects

Uses of spider silk

· Tribal people in Australia and Papua New Guinea use the web of Nephila sp. to make fishing nets.

· Some tribal people in Maharashtra mix spider silk with jaggery to make native medicine to control fever.

· Spider silk is used as a healing agent in Unani medicine.

Some common spiders of the Western Ghats

Spider facts

· All spiders are carnivorous and feed only on living prey.

· Spider silk is a kind of protein, used not only for trapping prey but in egg cases, nest lining and as a food source.

· All spiders are poisonous to their prey. Only a few are highly venomous and can kill a human being.

· Spiders may live from several months to ten years in their natural habitats.

· All spiders are solitary except for the group known as "social web spiders", which live in colonies.

· Certain species of sunbirds use the nests of social web spiders for their nests.

Spider myths

The term Arachnidae is derived from the Greek Arachne, meaning spider. The legendary Arachne wove exquisite tapestries. She was invited to a weaving competition with the Goddess Athene, whom she defeated. The enraged Athene tore the tapestry and Arachne killed herself. It is said that Athene changed Arachne to a spider so that she could continue spinning beautiful tapestries!

Spiders are also mentioned in Hindu mythology as worshippers and protectors of Lord Shiva.

The jumping spider anchors itself to the ground with a silk thread before it jumps on its prey.

The jumping spider

By R. Bhanumati