Spiders are not insects but Arachnids and members of the order Araneae. They are quickly recognized by their eight legs and multiple eyes. Unlike insects, they have only two parts to their bodies instead of three and they never have wings.
Our planet is home to more than 45,000 species of spider. They can be as small as the head of a pin or the size of a large dinner plate at 10 inches across. Spiders live in a wide range of habitats, from ground level to the tops of trees and from damp rainforests to arid deserts.
Spiders are beneficial to mankind. They do not spread disease and are estimated to eat between 400 and 800 million tons of insects a year worldwide. However, they are considered a nuisance pest by the many people who have a fear of spiders. In addition, their unsightly webs, if left, can harm property values and damage the reputation of a business.
Spiders obtain their food in many ways. Examples include:
- Orb spiders and many others spin elaborate webs to catch their prey.
- Trapdoor spiders hide in the opening of a tunnel to ambush passing insects.
- Jumping spiders are superb hunters.
- Bolas spiders throw their webs like nets to snag a meal.
Spiders do not undergo complete metamorphosis. Newly hatched spiderlings look like miniature adults. As they grow, they must shed their exoskeleton as it does not grow with them. A spider will molt several times during its lifetime.
After mating, a female will produce one or more egg sacs. These silken sacs are a protective casing which keeps the humidity inside stable during the development of the eggs. The shape and size of the egg sac can help identify the type of spider. The number of eggs in each sac varies by species, from just a few to over a thousand.
The many spider species around the world have developed different survival strategies. Some females hide their egg sacs, while others carry them. The time it takes for the eggs to hatch also varies. In cooler climates, eggs often overwinter. Others may hatch after only a few weeks.