You’re right, of course, but you have to remember that exoticdoc2 isn’t really interested in how biology works. That would involve studying the evidence and learning how science works; he’s already decided, however, to go with “magic man done it” and not just any magic man, but rather the magic man in his particular interpretation of one of the arbitrarily chosen old pre-scientific books of myths that were so common in the ancient world.
But, back to the subject. Actually, only some spiders are cannibalistic. But they are all fascinating. Besides an introductory book I’ve mentioned a few times before, Lynne Kelly’s “Spiders: Learning to Love Them,” I’m currently reading “Spider Silk” by one of the world’s leading arachnologists, Catherine L. Craig. The book is subtitled “Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating” and goes into a bit more detail (but not so much that a scientifically-literate person can’t follow it). Truly fascinating stuff—both the various silks and the different webs made from them, as well as the evolution of the entire system, with numerous references to the primary research sources in the footnotes and bibliography.