I've basically focused on the current biome for this one, but i guess it could be implemented anywhere really haa!
Scavenger Lair- they appear in the sides of mountains, and if left for a while, they begin to spawn eggs. As time passes, more eggs spawn, until it reaches a pre-defined maximum.
Scavenger Larvae- each egg hatches two or three of these slug-like creatures. They target carrots, but will eat anything on ground level. They leave behind a harmful slime which remains for a short time before disappearing. The Larvae retreat shortly before dusk.
Scavenger Fly- If the Scavenger larvae are left to thrive, or not all are removed, they will develop into the Scavenger fly. these pests will attack in swarms of five or six, and eat anything they can get. Tomatoes, carrots, they will even break the glass of greenhouses, and weaken doors to get at the food within. They cause no direct harm to players, but can make their dwelling quite vulnerable to...other....things.......
I'd really like to know what everyone thinks about this idea. I think it would add depth to the survival area of the game, but i don't want to frustrate people too much. hee hee!