Arachin body types, subspecies, and locations of major populations, along with racial information.
Arachin's native tongue is actually comprised of clicks, purring noises, low rumbles, and gestures. Speaking "common" tongue as a second language. Most other species don't know Arachin unless they interact with one on a daily bases as it is difficult for other Races to recreate it.
Scarabin and Dromos seem to be the only races who actively learn it and can speak it properly.
Pygmy Arachin speak the same language but with a different dialect. They use high pitched sounds instead of low rumbles. Whistling and hooting instead of hissing and growling.
Arachins can have pincers. Also size limitations. The larger the Arachin... the less he has the ability to climb any surface. Loment's size and down can climb any surface, even smooth ones. Loe Kanum cannot climb a surface unless there are holds for him to put his 'legs' in.
Any Arachnid based Meddian that does NOT have a Tail is an Arachin. It cannot be a Dromos unless there is an obvious injury leading to the lack of tail.