Most of us simply never notice them because spider mites are only a problem when their populations escalate. Unlike spider mites, feeding spiders have no interest in plants. Yet, it's startling how frequently people have to be reminded that a spider spins a web to catch insects. Perhaps E.B. White said it best in the classic children's book Charlotte's Web . Flies, bugs, grasshoppers, choice beetles, moths, butterflies, tasty cockroaches, gnats, midges, daddy longlegs, centipedes, mosquitoes, crickets - anything that is careless enough to get caught in my web.
Size is the critical issue for telling the difference.
Spider mites are extremely small. Well, a couple of spider mites could be dancing a waltz on the period at the end of this sentence without having to set foot onto the non-inked portion of the page. Keep this in mind the next time you notice webs in your trees. Obviously the web emanating from the back end of something as tiny as a spider mite is going to be extraordinarily fine. If you can see a distinct individual strand of webbing you are most likely dealing with a spider, not a spider mite.