One of the first species to join the Federation, the Andorians are a violent warrior race. Unlike the Klingons they tend to fight for purely practical gain rather than for personal honour or glory. Andorian culture stresses discipline and self control, and this can make them appear unsympathetic at times. Physically, Andorians are humanoids similar to many in the Federation. They have distinctive blue skin and white hair, but the most obvious difference lies in their antenna; these are an extension of the nasal cavity, giving the Andorians an outstanding sense of smell and a high sensitivity to changes in air temperature, pressure or composition. The basis of the Andorian culture is the Co-operative. This is a group of up to 100 families who have pooled their resources in a clan like structure. As members reach maturity they can choose to remain within the Co-operative or strike out on their own, forming a new unit or joining with another. Those who cannot decide on a Co-operative tend to become outcasts within Andorian society. The Andorians have no world government - the Supreme Co-operative represents them in the Federation, but it only covers some 30% of the population. As a result, many Andorians do not regard themselves to be Federation members at all. About 40% of the Andorian population live on the inland plains. These tend to be semi-nomadic, while the majority which live on the coast are city dwellers. The two groups have become increasingly isolated from one another over the last hundred years.The home planet of the Andorians is called Fesoan in their language, or Andor by the Federation. It is a class M planet, the eighth of nine in the Epsilon Indi system. It is a large, hot dry world with little surface water, and a gravity of 0.9g. There are, vast underground water reserves which feed surface geysers heated by geothermal energy. Oases surrounding these geysers are the centres of the planet's main population areas, since the great majority of Andor's plant life thrives where subsurface water is plentiful. The population is only in the tens of millions; as a result, Andorians are a relatively rare sight in the Federation.