"Gak! Cough! I just swallowed a bug."
Spiders of the moonlight, weaving webs of smoke, mist, and moonbeams.
Sometimes, someone is watching in the middle of the night.
Rats the size of cats, these insectivores are tree-top hunters. While they are useful to farmers and people, they are considered pests.
It is whispered at harvest bonfires that sometimes swarms will combine into a monstrously huge pile of Black Leaf Bugs, able to instantly stop anything it comes across. What is left explodes in a shower of maggots.
On a location with numerous webs, and at least one big spider, there is a something inside a cocoon. It is humanoid in shape, still moving. If the heroes free it (not before they kill or drive away the spiders), they meet a ... zombie!
The poor zombie wandered the dungeon alone, and tried to kill a big living creature (= a spider). The spider used the usual treatment, even if this victim did not look tasty. The zombie can be easily killed as any other zombie. It got but several doses of spider-poison, so can be something worth if it is extracted. You can mention to a druid or ranger the fact the spider had no poison anymore.