The Visitors - usually referred as Vs - are an extraterrestrial race of humanoids outwardly appearing to be much like Earth's Homo sapiens, but later discovered to be reptilians covering their bodies in cloned Human flesh.
Biology[]
A Visitor eye.
When the Visitors first arrived on Earth, several reporters tried to ask Anna why they looked so similar to Humans (for that matter, attractive Humans), given that Human scientists have calculated that the probability of alien life evolving to be exactly like Humans is extremely low. Anna brushes this off by saying that her scientists could explain. Apparently, the cover-story that the Visitors propagate is that through convergent evolution, intelligent life just happens to evolve towards the Human form.
Underneath their disguises, they have scaly skin, slit eyes, and a row of sharp retractable teeth.
The Vs seem to have specialized roles pointing to a caste system. They are highly destructive when sent to kill something and can sense heartbeats. This all fits into the idea that they are bred for combat. Trackers are similar to soldiers who have heightened senses, and camouflage, and can track people.
Anna shows her fangs after mating.
Visitors are apparently genetically similar enough to Humans that cross-breeding to create hybrids is possible. This would confirm that they are carbon-based, have left-handed protein and right-handed DNA, and probably have the same chromosome number. They have a large amount of sulphate naturally occurring in their body, as a Human woman would need this sulphate to make it through a hybrid pregnancy.
The exact dietary needs of the Visitors have yet to be revealed, though they can apparently survive on Human food if they need to.
A pregnant female visitor (or a Human female pregnant with a hybrid) experiences a massive increase in appetite - upon impregnating herself to spawn a larger army, Anna immediately devoured her mate after mating. The eggs of the Visitors don't have an eggshell but float in a pool of liquid, it seems that laying thousands of eggs is a norm for the queen. The eggs mature in a matter of weeks and become extremely engorged.
Visitor skin under the fake Human skin.
In reality, the Visitors are a race of reptilian humanoids. On the universal scale, they're still fairly close to Humans - in the sense that they're humanoid vertebrates as opposed to insect-men, and have mostly the same life support requirements (breathing oxygen, similar gravity, comparable tolerances to heat/cold).
However, the Visitors are still far from the attractive Humans they present themselves as. The Visitors have actually been sending intelligence gathering missions to Earth for decades (at least since the 1950s), gathering genetic samples to eventually make cloned Human skin-suits which they wear as a disguise. These suits are apparently connected to their central nervous system, allowing for complete control and sensation in this outer layer. As opposed to simply a costume, this disguise is living flesh, but not part of the actual organism. They are capable of healing on their own, though Visitor technology can be used to enhance the rate at which it does. They apparently have openings under the fingernails for claws to come out, but it's unknown if this applies to everyone or just females.
Culture and society[]
The Visitors and humanity established diplomatic relations a few hours following Anna's broadcast from the Motherships with world leaders. Visitor Embassies were established across the globe, where the Visitors would be allowed on Earth and the Peace Ambassador Programs could be headquartered. After several weeks, countries began opening their borders to the Visitors. The first countries were Mexico and Japan, followed by the United States, who issued special Visitor visas to over 100 Visitors.
The Visitors have their own language, which consists of 41 characters and ten numerals. It is often used on computer screens, and in signs posted around their facilities. Facilities that are open to humanity often have bilingual signs.
Technology[]
The Visitors are far more technologically advanced than humanity. The Visitors have the ability to cure over 65 different Earth diseases, can manipulate gravity, have holograms, synthetic flesh, revolutionary power and propulsion systems, hallucinatory torture devices, and more). Anna stated the Visitors would share this technology with Earth.
The Visitors use city-sized vessels to journey to Earth, known as a Mothership. There are over 29 Motherships around the world, in the cities of New York, Los Angeles, Mexico, Rio de Janeiro, London, Paris, Madrid, Moscow, Cairo, Tokyo, Shanghai, Sydney, Hong Kong and Florence, among others.
They use much smaller vessels for transport from the Mothership to Earth. The Visitors have also pioneered a device known as a Seeker, a gravity-resisting orb used to seek and destroy its victims.