Spiders are generally feared by humans because of their creepy appearance and tendency to build webs in homes. However, not all spiders are harmful to humans. In fact, some spiders can be beneficial, like the common house spider which helps control pests. But there are some spider species that can be dangerous, and their bites can cause serious health problems.
Spiders vary greatly in size, with some of the smallest being just a few millimeters in length while the largest can have a leg span of up to 30 centimeters (12 inches). The vast majority of spiders are harmless to humans and many are actually beneficial, preying on insects that are considered pests. However, there are a few species that can be dangerous to humans, particularly if they are venomous.