Orb weaving spiders are named for their interesting behaviour of collecting "balloons" of semen and hanging them around their nest for later consumption. The webbing itself is infused with mana which causes it to rhythmically vibrate and squeeze around anything it encases. With a healthy dose of aphrodisiac venom, it's impossible for any adventurer to resist the pleasure. They say exposure therapy is one of the most effective methods of overcoming fears. In this case, the therapy is so effective that eventually cocooned boys never want to leave~