How Did Spiders Evolve?

Spiders have a fascinating history. They have staked claim on land for hundreds of millions of years, and they are likely to do so for many more. The ancestors of spiders were aquatic chelicerates, but they eventually made the move to land. During their evolution, they have undergone numerous changes in anatomy and reproductive behavior.

The first web-building spiders appeared around 200 million years ago. This was during the Upper Carboniferous period. These early spiders had fangs that struck vertically.

Some of these early spiders used spinnerets to produce silk. They may have used silk to prevent drying of their gills, or they may have wrapped their eggs in silk to discourage predators.

Scientists think that this behavior evolved because spiders had to sense air currents and other environmental conditions. Since spiders can detect air currents, they would be able to locate prey that was carried sideways. In addition, they would also be able to sense an insect being carried by the wind.

Sheet-like webs differ from orb webs in that the spider weaves interconnected threads and uses silk to make the web. The spiders of different islands may have colonized and formed separate populations, which then diversified into different species.

A group of researchers analyzed genetic data from 12 spider families. Four new species were discovered.

Several studies have suggested that spiders have a complicated evolutionary history. One theory suggests that spiders are descended from arachnids with tails. Attercopus fimbriuguis, the proto-spider, had an opening on its abdomen that scientists think was a silk gland. Another theory suggests that spiders used silk to produce webs.