Another way to determine what type of spider you're looking at is to look at the legs, along with the eye formation. Different spider families have different sized and shaped legs. Orb-weavers in both Tetragnathidae and Araneidae, have the leg arrangements of 1, 2, 4, 3 or 1, 4, 2, 3, where the 3rd pair of legs are the shortest while the first pair of legs are the longest. The family Theridiidae also have a similar leg arrangement but their eyes are very different from orb-weavers, for instance.