Bee's and wasps or hornets
Bee's are neutral but get extremely aggressive once the player destroys the hive to get honeycomb (either to heal or for side quest).
wasps are a tiny bit bigger than Bee's but instead are aggressive and will attack on sight and use a mild aphrodisiac on there stinger.
Hornets are as big as the rats (in this game) and will follow you until you get inside a building or integrate with it.
I think that's a good idea.