Bloodflies

Bloodflies are flying parasitic insects found in Karnaca in Dishonored 2. Native to Serkonos, they build fleshy nests with many holes within the bodies of the dead and in abandoned houses.

Bloodflies guard their nests viciously, and attack anything that comes too close. These nests, grown from their victims' corpses, are highly susceptible to fire, and occasionally Grand Guard squads are dispatched to burn out or "smoke-flash" infestations.

Later on in their life cycle, bloodflies lose their wings, becoming beetles and are no longer aggressive. These beetles have many beneficial qualities, especially to agriculture. Without them, many crops across Serkonos would suffer, leading to decreased yield.

Bloodflies are capable of spreading Bloodfly Fever, a disease that Alexandria Hypatia attempts to treat in her laboratory at Addermire Institute. Late-stage sufferers of the fever will sometimes become compelled to tend to and protect bloodfly nests until they expire, ultimately being colonized and turned into a new nest themselves.

Dishonored 2
In 1852, due to a significant increase in bloodfly population across Serkonos, Duke Luca Abele issued an edict in order to contain the situation. The edict consists of a number of regulations that require citizens to report bloodfly nest locations to the Grand Guard, give full cooperation to smoke-flashing crews, follow guidelines when attempting burial or cremation of human remains, and burn dead livestock only at approved locations. The Duke, however, prohibited anyone to refer to the problem as an epidemic, calling it "the bloodfly concern" instead.

Despite the hazard of clearing bloodfly nests, Luca Abele later decided to stop funding the smoke-flashing crews. This forced the workers to enter infested buildings and use inefficient tools such as Orbon Rum bottles, which led to higher casualties and even more bodies for bloodflies to lay eggs. Only those who are desperate enough would sign up for this job, hoping to make some quick coins by collecting blood amber. The Grand Guard, however, would force the workers to pay some obscure taxes if they are discovered to possess amber.

Combat and Behavior
While individual bloodflies are not aggressive, they hunt in groups as small as three. Aggressive behavior is usually indicated by a red glow of a bloodfly's body and louder buzzing, while an inert bloodfly is more subdued in both color and sound. Aggressive bloodflies will be provoked to attack by noise, close proximity to the nest - or to the swarm, if the bloodflies are not tied to a nest -, or a nest keeper's call.

A bloodfly nest will keep replenishing the swarm that protects it until the nest is destroyed. Once that is done, the protecting swarm will usually cease attacks, scatter and become harmless, unless there is another nest in the immediate vicinity. It may be advisable or necessary to deal with bloodflies without destroying the nest first, especially when the swarm is not tied to a nest. Most supernatural abilities are of limited use against bloodflies.
 * The nests are highly susceptible to fire, and hitting them with an incendiary bolt or explosive bottle will not only destroy all nests caught in the effect, but also draw in all nearby bloodflies and burn them as well, dispatching both the nest and the swarm in one strike. Equipping the Hot Cocktail and Firestarter bone charms makes this strategy even more effective.
 * It is possible to run up to a nest, smash any bloodflies in the way with the sword while doing so, and then destroy the nest with the sword without being stung. Since this strategy relies on swiftly dispatching all involved bloodflies or their nest, it is not advisable with more than one nest or swarm nearby. Otherwise, it is one of the few known ways to destroy a nest without spending any resources or getting injured.
 * Besides fire and the sword, nests can be destroyed with pistol bullets, Windblast, whale oil tanks, and grenades.
 * Grenades are particularly effective with the upgrade The Expansive Lady, allowing the user to take out large clusters of nests at once.
 * If the Crimson Painter upgrade for the pistol was purchased, a pistol bullet can simultaneously take out a cluster of bloodflies.
 * Bloodfly-infested corpses do not function as nests, although they share some similarities. While they spawn a swarm of bloodflies once the infestation is complete and the swarm will follow and protect the body, damaging the body does nothing to deter or scatter the swarm, and the infested corpse does not replenish the swarm.
 * Howling bolts and grenades are particularly effective against bloodfly swarms, killing all insects caught in the effect. Equipping the Resounding Shriek bone charm is helpful there; stacking the effect may allow clearing an entire room or hallway of bloodflies with a single howling bolt.
 * Alternatively, bloodflies can be smashed and the swarm decimated with a succession of quick sword strikes. The Whirlwind bone charm helps reducing the risks of this strategy.
 * Incendiary bolts and explosive bottles don't hit many bloodflies without a nest to draw them in and spread the effect, limiting their usefulness against swarms without a nest.
 * Bloodflies prioritize laying eggs in a body over attacking intruders or defending the nest, so bringing a body and throwing it to close proximity of the bloodflies will distract them long enough to safely dispatch the swarm even from up close and destroy the nest.
 * Windblast pushes bloodflies back, but rarely kills them.
 * Devouring Swarm distracts some bloodflies, but usually not enough of them to make an approach safe.
 * A Doppelgänger with the Deadly Shade Upgrade fights bloodflies, but is ineffectual at doing so and will be quickly overwhelmed by a single swarm.
 * Bloodflies ignore Emily Kaldwin during Shadow Walk, allowing her to get close to nests that aren't easily accessible or to safely pass through bloodfly-infested passages. Possessing a bloodfly or stopping time allows similar results for Corvo Attano.

Supernatural Abilities
The Bloodfly Swarm upgrade availble for Shadow Kill in Dishonored 2 transforms enemies killed in combat into bloodflies as they die.

Related Bone Charms

 * Bitter Blood - Bloodflies attack at slightly shorter distances, closer to nests.
 * Blood Sacrifice - Killing bloodflies or rats restores Health.
 * Carrion Killer - Killing rats or bloodflies boosts Adrenaline.
 * Savage Scream - Sometimes a Nest Keeper's scream kills some surrounding bloodflies.
 * Spiritual Sacrifice - Killing bloodflies or rats restores Mana.
 * Bloodfly Alchemy - An enemy's initial ranged attack is transformed into bloodflies.

Trivia

 * Venom glands of bloodflies are one ingredient of the Addermire Solution.
 * The nests bloodflies create sometimes contain blood amber, a valuable material used to create statues.
 * Rats and bloodflies are natural enemies: rats eat bloodfly larvae while bloodflies lay eggs on rats. It is said that bloodflies are one of the factors that kept the rat plague from spreading in Serkonos.
 * Anton Sokolov believes bloodflies originated from the Pandyssian Continent.