A key component of animal survival is the ability to acquire food. Because spiders are predators, they kill and eat insects and even other spiders. How they go about doing this varies base upon whether the spider is a web-building spider or a hunting spider, both of which capture prey by playing to their physical strengths.
As a rule, hunting spiders have better eyesight than web-building spiders. As such, hunting spiders will often lie in wait until their prey is within sight. Some spiders can see up to eight inches away, which is impressive on a scalar level. Web-building spiders, on the other hand, usually have poorer visions, which is one reason they spin webs to snare prey as it passes.
As with eyesight, hunting spiders are usually faster than web-building spiders. This speed is perhaps the hunting spider's biggest asset. As it spies its prey, the hunting spider can than move quickly to attack. Some spiders crawl very quickly, while others jump to cover large distances in a short period. As web-building spiders are usually slower moving, their webs' ability to hold prey in position until these spiders get to the prey is extremely effective.
Web-building spiders rely on their ability to sense vibration to know when they have snared prey in their webs. Once they sense the movement, they descend from an area near the perimeter of the web to meet their prey. Hunting spiders, because of their keen eyesight and speed are much less reliant on the need to sense vibrations and, as such, it plays a much lesser role in their ability to acquire food.
A commons misconception about spiders is that hunting spiders hunt because they can't produce silk. In fact, all spiders can produce silk. We tend to only notice this with web-building spiders because it is more vital to their basic survival. Aside from using silk to build webs, young spiders will release long strings of silk and let the wind catch that silk, this carrying them to new locations. This process is called ballooning.
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