Spider webs have existed for at least 100 million years, as witnessed in a rare find of Early Cretaceous amber from Sussex, southern England. Many spiders build webs specifically to catch insects to eat. However, not all spiders catch their prey in webs, and some do not build webs at all. "Spider web" is typically used to refer to a web that is apparently still in use (i. e. clean), whereas "cobweb" refers to abandoned (i. e. dusty) webs. However, the word "cobweb" is also used by biologists to describe the tangled three-dimensional web of some spiders of the Theridiidae family. While this large family is known as the cobweb spiders, they actually have a huge range of web architectures; other names for this spider family include tangle-web spiders and comb-footed spiders.