The Black Widow spider, for example, which is found in South America is the most poisonous of all spiders. The female of the species, whose poison is strong enough to kill a human being, often kills and eats the male after mating and is thus aptly named the Black Widow. This spider is shiny black in colour with a red hour glass mark on the ventricle side of the abdomen. Fortunately, there are no spiders in India which can seriously harm human beings.
There are about 30,000 species of spiders in the world. They have been found upto a height of 23,000 feet up Mount Everest as well as underwater.
Almost all spiders are carnivorous. They can eat insects, small birds, mammals and reptiles, including poisonous snakes and other spiders, which they first subdue with their poison. They inject their prey with a highly lethal venom and, having no teeth, suck out the liquid from inside their prey. Large spiders with longer and powerful jaws may eat part of or even the whole of their prey. Spiders can live without food from a few weeks upto three months, depending on species, size, and age. They obtain liquid from their food and thus do not need water.
Many spiders spin webs to capture their prey. However spiders also have other means of capturing their prey. Some spiders spit a sticky web onto their prey. Others live in burrows with trapdoors. Whenever they feel hungry they come out and catch an unsuspecting insect. One species attaches a sticky drop to one end of its silken thread and holds it with its first three pairs of legs. When an insect passes by, the spider waves the thread at the insect and ropes it in, as it were.
Some spiders sit on flowers and catch insects that come to collect nectar. Others spin a small web, hold it with their first few pairs of appendages and then throw it on insects passing below them. Still others feed on other spiders only and are called pirate spiders. A few spiders live on the webs of other spiders: they are too small to be eaten by their host. They eat the small prey that get caught in the web, thus keeping it tidy.
Spiders also have amazing defence mechanisms. Some spiders camouflage themselves as a bird dropping. Others, as a dried yellow or black rotting leaf or twig. And yet others resemble ants which are often rejected by birds, reptiles and other insects. Some are even able to change colour and shape, to some extent, to match their surroundings. Some species build zigzag white coloured threads in their webs which are visible to birds who avoid flying through the webs and damaging them.
The male spider is smaller than the female, and is thus liable to be eaten by his mate. So, the male uses many tactics to prevent his being devoured by his mate. In some cases the male drums or pulls at the strings of the web in a special code to announce that he is not a prey or an enemy, but a sexual object.
Some spiders offer their mate a gift such as a juicy fly, wrapped in silk. But it may well be taken back after mating and offered to another female. Sometimes a male may even offer the female the empty husk of an insect. Sometimes the male loosely binds the female with silk to immobilize her before mating. Some species of male spiders may patiently wait near the web of a female spider for weeks until she has caught a prey, and then mate with her while she is busy feeding on the prey. Sometimes, the male is so small compared to the female that the female is practically unaware of him while mating and this gives him protection.
Most spiders are solitary in nature. Each one builds its own separate web. If one spider falls by mistake into another web, the bigger spider will eat the smaller spider. However, there are some spiders called social spiders that live together in one web. Sometimes there may be hundreds or even thousands of adults and young ones living in one web. Even if a single prey is caught (such as a small fly), all the spiders will share the meal.
Spiders multiply very rapidly. After mating, an egg sac is constructed and the internally fertilized eggs laid inside the egg sac which is carried by the female with her palps and fangs. Fertilization of eggs may be internal or external depending on the species. Within 15 to 20 days, 80% of the eggs hatch. (The eggs hatch into young spiderlings. The new born spiders are similar to their parents, only smaller. The spiderlings moult to mature.) After a gap of one week to ten days the next batch of eggs is laid in a fresh egg sac, and fertilised with the help of stored sperm. The female can do this three to four times without mating with another male, although she will readily mate with a male after the laying of every batch of eggs.