The Kreen are so nearsighted that Humans would consider them almost blind. In compensation, they have several different forms of vibrational senses (including a complete tectonic awareness and high-frequency doppler sonar), a sense of magnetic fields, an electrical sense, highly-sophisticated biochemical detection surpassing even the Terran bloodhound, touch pads with hindredth-millimeter sensitivity, a gravity-balance sense accurate to one part in a billion . . . Kreen perception approaches clairvoyance.
The Kreen have one additional advantage: their society. Multiplexing on all sensory channels, they are capable of communication that approaches telepathic rapport. Kreen intelligence increases as a power of the number of individuals involved. Kreen individuals in rapport take on specific roles: communicator, sensor, manipulator, memorizer. Three Kreen are about as intelligent as a smart Human -- this is the minimum number of Kreen that can achieve self-awareness.
A Kreen "clan," containing between three and 729 individuals, is called a chaio. The chaio, corresponding in many ways to the Human family, is the basic unit of Kreen society. The traditional maximum number for a chaio is 729 (three-to-the-sixth) -- above that number, a chaio will naturally divide into two or more smaller groups.
A group of chaios is called a riako, and can involve up to hudnreds of thousands or even millions -- and reach the mental ability (although not quite the speed) of a supercomputer.
The most notable example of a riako is the ruling riako, called the Miethara, which gave its name to the Kreen empire.
Typically a Kreen individual reaches sexual maturity at 4-7 Terran years, and at that time decides to ally with a particular chaio. This is often a mutual decision. Thereafter, individuals frequently move from chaio to chaio at the whim of the chaio.
Kreen philosophy has a keen awareness of the individual and
individuality -- but it is only within a chaio that the individual
is able to apprehend its own existence.
The Kreen come in three different genders: female(XX), male (XY),
and kemale(XZ). All three must be present for intercourse. The
kemale and male both impregnate the female, and hormones in the
spermatic fluid of both combine to make the ovum receptive to
conception. The ovum is impregnated by either a sperm from the
male, or a sperm from the kemale, so only two of the three "parents"
actually contribute genetic material to each offspring -- but
since the Kreen give birth to litters of 3-8 pups, the mix is
usually fairly good. Births average 50% female, 25% male, and
25% kemale.
Kreen females bear their litters live and in the context of the chaio. All intercourse is carried on freely among all eligible male/kemale/female triplets -- in fact, intercourse for the Kreen is a social matter, most closely resembling the orgies of ancient Rome.