When facing the cuckoos, it is best to remember three things. One, that your life means nothing to them. Two, that they can—and will, given the slightest opportunity—make themselves the center of your world. And three, that they are not in any way human, no matter how human they may look, and they will not regret anything they choose to do to you.
We don't know where they come from; they do not come from here. They show genetic similarities with the Apraxis wasps, despite being as far from them in morphology as is physically possible. They are the sole known representatives of order Apateprosopo, meaning "the face of deceit." They lie with their faces, which make them look like humans, while they remain impossibly alien within. And they lie with their actions. The cuckoos are ambush predators, infiltrators, and destroyers on a level that is almost unknown in other species. Thank God for that.
The existence of the cuckoos has been suspected for centuries, but was not confirmed until Alexander Healy began connecting seemingly unrelated events with the movements of known Apraxis hives. The cuckoo remains the only predator feared by the Apraxis. Given the Apraxis themselves, this should tell you something about how dangerous the cuckoos are. If encountered, shoot on sight, and scorch the earth behind you.
BIOLOGY
Biologically speaking, the cuckoos are mammals. They have three bones in their inner ears, they have hair, and they have mammary glands which they can use to feed their young, even if they generally don't choose to do so. These are the only requirements of class Mammalia.
The cuckoos also have clear blood which is similar to antifreeze in its general properties and consistency, and decentralized circulatory systems which function through a constant series of low muscular pulses. They are, quite literally, heartless. This charming bit of over-the-top symbolism aside, their general physiology and genetic similarities to the Apraxis wasp have caused us to conclude that, while they are mammals, they evolved not from apes, but from a complex form of parasitic wasp.
They just get better and better, don't they?
Cuckoos are mildly allergic to most forms of insecticides, which seems like it should be more useful than it is; most normal humans will also react poorly to being shot in the face with Raid. Cuckoos bear live young, and have a very low birth rate, largely because they seem to dislike each other almost as much as we dislike them. Their lifespans are close to or in excess of the human norm. There are no known illnesses which affect the cuckoos. Bastards.
Did we mention that they're telepathic?
PSYCHIC POWERS
Cuckoos are both projective and receptive telepaths. This wouldn't be such a problem if they didn't constantly project a field of "I belong here." A cuckoo who breaks into your home will be your sister, your husband, your parent, or your child in a matter of seconds. Angela Baker, one of our two resident experts on the species, says that this impulse can be controlled to a small degree, but will activate automatically if the cuckoo is stressed or frightened. Very few of them can control it. Very few ever bother to try.
Angela also confirms that cuckoos should be shot on sight. As she is a cuckoo, this is not a good sign for peaceful future relations.
The standard hunting pattern of the cuckoo is simple. They isolate their prey and become part of their lives, convincing their victims that they not only belong, they have always belonged. This accomplished, they will drain those victims of all resources, often causing intentional chaos immediately before leaving those victims to suffer the consequences. They don't eat human flesh, but in a very real way, they eat human lives.
DESCRIPTION
Externally, cuckoos look exactly like people. They are more homogeneous than humans; all cuckoos possess pale skin, dark hair, and unnaturally blue eyes. People tend to remember them as attractive. Given that they are telepathic and manipulate the perceptions of those around them, this is questionable.
INSANITY
It has been proposed by Angela Baker that all cuckoos are born insane, not because of any biological impulse, but because their mothers were telepathic, and their mothers were insane. She has tested this theory on her adopted daughter, Sarah Zellaby, removing the majority of the pre-natal damage from Sarah's mind. The result has been a sane, stable, relatively functional individual (sorry about the "relatively," Sarah). Unfortunately, this is not a solution which can be implemented on a wide scale.
Pictured below is Sarah, looking characteristically mortified by her species, and an unidentified male cuckoo in the process of telepathically influencing a human victim. Due to the lack of physical variation between cuckoos, they can be taken as good examples of the species.
Artwork by Kory Bing.