If the encounter should have webs thrown at the characters rather than them stumbling into nets of webs you could use giant insects in place of spiders. This will keep the theme of a real life animal made into a giant monster.

Example: Giant moths that spin cocoons out of silk to trap PCs and have a poisonous dust that emits from them.

OR: Giant ants that craft devious traps out of leaves.

If the encounter should have immobilization of the characters you could use giant insects in place of spiders. This will keep the theme of real life animals made into giant monsters.

Example: Giant moths that spin cocoons out of silk to trap PCs and have a poisonous dust that emits from them.

OR: Giant ants that craft devious traps out of leaves. PCs could get immobilized in these traps they stumble in with a different look to webs . If needed for the story the giant ant colony could have moved in and wiped out the giant spiders...