Infestation

Infestations are a random event in Rimworld.

Spawning

During this event, insect hives spawn in an area below an Overhead Mountain. Soon, insects will pop out of these hives to defend their hive, and will aggressively chase down any perceived threats such as your colonists.

If the hives are kept well, they will reproduce, spawning more hives and insects. If all insects are killed, the hives will deteriorate due to lack of maintenance.

Infestations will only spawn within 30 tiles of a colony structure. They cannot spawn in an area that is below -17°C (1°F) or on a tile that is occupied by a piece of furniture.

Hives prefer to spawn in areas that are deep within the mountain. Other factors, such as rock walls and light have some influence on their spawn point of choice. Temperatures under -8°C gradually reduce the spawn chances, with the chance dropping to zero at -17°C. Neither heat nor floors have any bearing on hive spawning.

Strategy

Infestations are most threatening in mountain bases, as they can spawn practically anywhere inside your base. They are much less harmful in other bases though, and can be considered as a normal-level threat.

When fighting an infestation always pay attention to any remaining hives. If you have 1 hive remaining which you totally forget about, soon the hive will reproduce and fill the area with insects.

Products

Hives bring glow pods that glow for 20 days (as long as they’re installed) and can be reinstalled, or sold for a paltry price. The 20 day lifespan of the glowpods corresponds with the cooldown on the infestation event.
Hives also produce insect Jelly in stacks of 20 every day or so, so if you could trap the hives via walls and doors, you could potentially farm the insect Jelly, though the insects are liable to digging out, and can threaten your colonists when they try to retrieve the insect jelly.