I had an idea for a new kind of spider. Maybe these already exist after some fashion.
Carrion spiders come in two varieties - the scavenger and the hunter. Both utilize the same method of capturing prey - they set up their webs or stalk their prey around a dead body that attracts insects and other scavengers.
Scavenger carrion spiders are the stalkers. They wander around the forest (or other environment) seeking dead fruit, plants, and animals and prey on the other insects that come to feed on the carrion. They are especially attracted to the smell of rotting flesh and so are sometimes fooled by carrion plants (indeed, the sight of dead scavenger carrion spiders is a good indication that the source of that terrible smell is a carrion plant).
Hunter carrion spiders are the trap setters. They do not seek out existing carrion but purposefully kill other creatures and leave them to rot in order to attract more food. Since they choose the where and the when of the carrion lure, they are able to set up webs to trap their prey rather than stalking and subduing it like their scavenger cousins.
The fun comes from the giant carrion spiders. Scavenger spiders set ambushes around dead bodies that fell to traps or combat and attack looting adventurers. Giant hunter spiders are deferential to shiny creatures as bait. A fat merchant with a dozen rings makes for a very enticing lure, both for looting adventurers as well as less intelligent beings. It is rumored that some hunter spiders are possessed of a malign intelligence and they use piles of treasure as bait.
Dung spiders are carrion spiders that hang around dung rather than kills. They are more numerous and better off from an evolutionary stand-point as dung is much more readily available.