Cellar spiders, also known as daddy longlegs, are common arachnids found in homes and buildings. They have long, thin legs and small bodies, typically measuring about 5 to 10 millimeters in length. These spiders prefer dark, damp areas like basements, cellars, and corners, where they build loose, tangled webs to catch their prey. Despite their appearance, cellar spiders are harmless to humans and are beneficial for controlling pest populations. They primarily feed on small insects, such as flies and mosquitoes, which they capture in their webs. Their presence can help reduce the number of unwanted pests in indoor environments.