Kloros

The Kloros are a spacefaring species of chlorine-breathing, colonial insectoids which at some point in their history made contact with Humans, resulting in a war between the two species.

Physically, they resemble large insects with a long, slender neck and a diminutive head containing a somewhat triangular-shaped proboscis and a pair of huge bug eyes. The brain, or the structure which acts as a brain, is located in the abdominal area, so that the head acts mainly as a support for the sensory organs and a decapitated Kloros will remain alive until presumably dying from inanition. Kloros are about as tall as a man and have a number of small tentacles protruding from their chest. Their blood is green. They breathe chlorine and oxygen is deadly for them.

Despite being in war against mankind, Kloros appear to have a respectable sense of morale and actually allow their prisoners to remain alive and in relative comfort, which is more that what can be said about how Humans treat Kloros prisoners. Kloros lack the concept of familial bond, but do have an analogous "group bond", as they evolved from colonial insectoids. They always travel with their groups and the relationships between members of each group are described as being similar to a parent-children relationship among Humans.

Behind the scenes
Kloros were featured in a short story by Isaac Asimov called C-Chute, which was first seen in the pulp sci-fi magazine Galaxy in 1951 and was later published in the book Nightfall and Other Stories. A radio adaptation of the story was also produced. Unlike the Cepheids from Blind Alley, there is no evidence to believe that Kloros exist or have existed in the Foundation universe, which encompasses most of Asimov's science fiction works. If C-Chute is to be regarded as part of that universe, then it is appropriate to suppose that the Kloros have either been destroyed or exiled from the Milky Way and their existence was eventually forgotten by humanity.