Infestation

Infestations are an event and a serious threat in which a number of hives are spawned, alongside insectoid defenders. They can happen randomly in your colony and ancient complexes or can be caused by a quest; quests will warn you if this is an outcome. Infestations can be very destructive, but leave behind valuable insect jelly and opens the opportunity for insect farming.

Natural Infestations

Blue squares show an area with a chance of infestations spawning.

Making 1x1 squares will usually eliminate bugs.
But if a 1x2 area has a single mountain roof - regardless if the other tile is mountain or not - then it can spawn infestations.

Natural infestations occur at a maximum of once every 20 days, but generally less often than raids, and only with a valid location.. Natural infestations require an area larger than 1x1, within 30 tiles of a colony structure, with at least one overhead mountain roof. They start from a single "valid" tile, which must have a temperature higher than -17 °C (1.4 °F). Temperatures under -8 °C (17.6 °F) will gradually reduce the spawn chances in that area. Infestations can appear from any valid tile, but tend to prefer areas that are very deep underground, with a slight preference for areas that are additionally warm, dark and unclean.

Infestations in ancient complexes will emerge after entering certain rooms but are usually smaller than a comparable colony hive and easier to defeat, avoid or redirect.

If generated from a quest with no valid location, infestations may spawn outside in the open.

Hives and insectoids will spawn within a given radius, regardless of whether those tiles are valid. A hive does not have to spawn on an infestation's center point. The initial size of an infestation is based on raid points, so infestations will get bigger as the game progresses. If the size of the event is larger than the "valid" space, it will happily expand to appear in nearby "invalid" areas, even if those areas are not directly connected. Infestations will stop expanding at a size of 30 hives or above, but letting infestations grow at all is usually inadvisable.

Defeating an infestation with hives grants a +4 Defeated insect hive mood buff to all pawns on the map. This buff lasts 10 days and stacks up to 5 times.

Behavior

Range at which insects will defend a hive

Insectoids (Megascarabs, Megaspiders and Spelopedes) will spawn near hives and spend their time roaming around them. They will attack and chase any intruder that comes within a 10-tile circular radius from the hive that spawned them, returning to their hives once the threat is gone. Insectoids will only attack creatures they can see, and will not attack while they are sleeping, provided they are not woken up.

They will randomly dig at stone and structures while wandering around their hives, potentially breaching into new areas.

If any of the insectoids are downed or damaged, the entire infestation will go after colonists on the map, attacking and breaking down structures in the process. Even if outside raiders or other factors (like hypothermic slowdown) down them, they will be aggressive. If insectoids don't see hostiles within 100 tiles, they will give up and return to their hives.

If the hives and insectoid colony are left intact, they will reproduce, progressively growing more numerous. If all megaspiders or spelopedes are killed, the hive(s) will start deteriorating due to lack of maintenance but will most likely replenish them before it's destroyed.

Other infestations

These events are called "infestations", but do not generate hives, meaning they do not share the behavior as shown above. They are immediately hostile to colonists and will attack like raiders do.

Too Deep: Infestation

Insectoid infestations can spawn from the use of a deep drill. Insectoids, but not hives, will pop out around the drill's area. These do not have the overhead mountain requirement like regular infestations. However, they are often smaller in number, and are unable to reproduce due to the lack of hive.

Wastepack infestations

Main article: Wastepack infestation

Wastepack infestations may appear whenever toxic wastepacks are destroyed.

When a wastepack infestation triggers, it creates stasis cocoons. When these cocoons are disturbed, or when a human walks within a set radius, the insects will appear. Wastepack infestations are more aggressive, attacking any hostiles, buildings, random junk and even wild animals they encounter.

Strategies

See also: Defense tactics#Infestations

Infestations are most threatening in mountain bases, as they can spawn practically anywhere inside your base. Outside a mountain, they are much less harmful - around a normal level threat. When fighting an infestation, always ensure you completely annihilate every hive. If even one is left, insectoids can keep spawning and leave you back where you started.

Since insectoids do not attack creatures while sleeping, it is possible to haul materials in and out of the area near their nests at night, including flammable material. This is however extremely risky, since attacking one of them, or doing construction near the insectoids, will wake them up. They also wake up when their individual need for rest has been filled, so be prepared (with all relevant items staged in a nearby stockpile) and act quickly once they're asleep.

Prevention

Wall filling

Hives require overhead mountain tiles to spawn naturally. Open caves and previous infestation locations can be walled in to move spawns away from your most important base areas, as long as they're not mountainous. As they require more than 1x1 of overhead mountain, you only need to build walls every second square. Only walls are capable of stopping infestations; columns and doors do not work. Note that an overhead mountain square next to an open "thin roof" area is also a valid spawn point.

Freezing

Because mountains are naturally well insulated and more stable in temperature, freezing your base is a potential, though fragile, strategy of protecting mountain bases in most biomes. By reducing the temperature of every tile of overhead mountain to -17 °C (1.4 °F), spawning can be prevented, however outside of the coldest biomes, this requires coolers and a significant amount of power. A solar flare, EMI dynamo, or similar can leave you open to infestations, so adequate defences are still recommended. The cold will also affect work speed, pawn moods, and potentially pawn health.

When spawn proofing a base, be thorough - even a single warm tile can cause a full infestation. If there is any valid tile, infestations can spread nearby into seemingly safe areas, even if there is a wall many tiles thick between.

Melee block

Melee block with frag grenades. Grenades not necessary.

With a few, well-armored melee colonists, insects can be very simple to deal with via a melee block tactic.

When designing a mountain base, keep these 6 tiles unblocked.

Use a chokepoint, such as in any doorway. Have 3 melee colonists behind the chokepoint, and any amount of ranged fighters behind them. If done correctly (see right), you should have 3 colonists fight 1 insect at a time. As insects are only melee enemies, this is a trivial way to dispatch of insects. Frag grenades are extremely effective, but are not required.

When designing a mountain base, you will want to create many chokepoints where you can melee block. You do not want to block colonists from standing on the 3 tiles behind the doorway, so place buildings away from the doorway. (See left)

Kiting

If insects spawn "in the open" (i.e. not inside a mountain), then kiting tactics are effective.

Even megascarabs, the fastest insect, are 82% as fast as a healthy baseline human (assuming no Pollution Stimulus). So it is possible to lure the insects, shoot with a ranged weapon, and retreat. After you get to a safe distance, have colonists shoot, and retreat again, repeating until all insects are killed. This strategy works well against Too Deep: Infestations, as well as any hive outside of your base.

Mitigation

Damage prevention

Keep expensive or complex production buildings in multiple locations, or seal them off with small compartments only large enough to contain the workbenches and associated facilities alone. Have multiple access points for rooms deep inside mountains so that colonists aren't trapped behind infestations.

Planned Infestations

An infestation spawn point trapped with incendiary IEDs, surrounded by stone walls and doors.

Insects are more likely to spawn in darkness, in "warm enough" temperatures, above -8°C (17.6°F). If you are able to ensure that there is only one valid infestation location on your base map, you can prepare this area to automatically trap and kill the insects with fire when they appear.

In a mountain base, you can create a "lure room". This will be a massive room that is warm, unlit, and dirty, very far away from your proper base. Since there will be many more valid tiles to spawn inside this room, infestations will most likely spawn there. You can then light this room on fire - see below for details.

Fire

One way of dealing with infestations is with fire. This consists of 2 parts:

1. Have a "lure" room - see above for details. In an outdoors base, it is likely that only 1-2 rooms have overhead mountain, meaning dedicated rooms can be built.
2. Light it on fire. Fill it with flammable objects like barricades and wood floor. You can either use molotov cocktails or IED incendiary traps to do the work.

Insects should die of heatstroke before they breach through 2-3 layers of door.

It is important to note that temperature is usually what kills insects, not the fire itself. Throwing molotovs outdoors is unlikely to be helpful: insects can walk past a burning wood floor with minimal damage, and even a direct molotov hit doesn't do much damage. Rather, it is the >300 °C (572 °F) heat that ignites the entire infestation and causes lethal levels of heatstroke. More gradual heatstroke will kill the bugs more slowly, but with less damage and anger from bugs compared to continuous burns. An area must be "indoors" in order to receive any sort of temperature change.

Insect AI

When attacked, insectoids will go after colonists without any walls between them first. This allows the insectoids to be lured away from their hives, chasing a runner colonist across the map. While they are away the hives can be destroyed. As long as hives are being damaged, the insectoids will keep chasing after colonists instead of returning to their hives. To keep the hive destroying pawns safe from having the insectoids' attention turned to them rather than the runner, a wall can first be built to block off the insectoids from the hives. Note that some new insectoids are likely to spawn at the hives during the process. Once all the hives are destroyed, the insectoids will wander the map like normal animals and soon starve to death.^{[Detail needed]}

Farming

See also: Hive#Farming

Insect hives in well defended and sufficiently distant colonies be farmed for large amounts of insect jelly. At high difficulty levels, spawned insects also give large amounts of insect meat.

An infestation event is considered active until all spawned hives are destroyed, with ongoing infestations preventing new ones from from occurring. If you can lure an infestation away from your colony into areas your colonists are prevented from accessing, you can prevent random infestations from occurring everywhere in your base, at the cost of a much more dangerous number of insects as it continues to grow.

However, infestations can also be limited in growth by removing suitable locations for new hives to expand into. Insects will dig through rocks and most structures^{[Detail needed]}, but will not expand new hives into spaces that are too far from their existing nests or unroofed. Ancient dangers can be potentially used for both finding a "decoy" hive, and limiting their available space, if you can distract the hostile bugs long enough to expose the majority of their nesting space to the sky. Smaller mountains may work as well, as bugs will almost always leave collapsed rocks alone for their own safety. Bugs in these circumstances should be given plenty of space to avoid encounters and walled off for the safety of travelers, and for the bugs themselves against more dangerous raids.