There are also presumably internal physiological differences, but these were not discussed in detail, however it is known that the color of their blood is blue. A small number of Nebari are natural hermaphrodites; the Nebari term for one is "androgyne." Being inherently incapable of conforming, androgynes are social exiles.
On their home planet, conformity is enforced by The Establishment. Young Nebari are tested and placed into a position in society based on their abilities, and are expected to conform. Nebari failing to conform to these strict controls are "stabilized" or "mind-cleansed" to fit in. There are two types of mind-cleansing: The first is permanent (except in isolated cases), but takes many cycles (years) to complete. The second is temporary, chemical-induced, and can be quickly applied, but does not work on all species; Nebari are immune to it, as are the Pilot species, and species such as Hynerians are affected for only a short time before their quick metabolisms rid their bodies of the drug. The Nebari Establishment claims to be acting for the "greater good" of everyone involved.
Few details are known of Nebari military capabilities, but they are believed to have destroyed the Zelbinion, a near-legendary Peacekeeper warship. The Nebari Salis claimed that this was achieved solely through the efforts of a Standard Host Ship, a vessel he classified as non-military. This information combined with the fact that Durka claimed a single shot from the phase cannons aboard the Nebari Transport craft Salis was transporting him and Chiana in was capable of aborting Moya's pregnancy, meaning penetrating the Leviathans outer and inner hull, with a single controlled shot, indicates that the Nebari might not militarilly powerful, but are highly advanced and capable of tremendous acts of violence when threatened. The Nebari Establishment also deliberately infected many of their own dissatisfied citizens with a delayed-action, sexually-transmitted biological agent and then gave them exit visas in the hopes that they would spread the disease around the galaxy. At some future time when the Establishment intentionally activates the contagion, it is designed to render infected individuals docile and obedient, thus smoothing the way for the Establishment's expansion. In fact, from their neural controls over their control collars, to their advanced medical technology, and the tremendous firepower possessed by all their vessels, The Nebari have proven themselves to be among the most technologically advanced governments, if not the most technologically advanced government, in the galaxy. As a final indication of the Nebari's real power is that fact that the short list of buyers for wormhole weapons given to John Crichton included only the Peacekeepers, the Scarrans, and the Nebari. This alone indicates that the Nebari are seen by outsiders who are familiar with them as being something of a power.
There is a revolutionary front in operation on the Nebari homeworld. It is by all given indications small in proportion to the total Nebari population, but given the technocratic nature of the Nebari government and its panopticonic observation and control of its citizens, the existence of any revolutionary front at all is no small indication of its strength and resilience. So far, members of the front have proven to be completely devoted to the cause and willing to sacrifice virtually anything for it. This is symptomatic of the Nebari's seemingly universal single mindedness.
Like a few other species such as Luxans, Nebari are able to withstand exposure to the vacuum of space for a limited period of time with no apparent ill effects ("Peacekeeper Wars: Part 1").
The most commonly seen Nebari on the show was regular Chiana. Apart from Chiana, Nebari appeared in the first season episode "Durka Returns," the second season episode "A Clockwork Nebari," and the third season episode "Fractures." Most of the information about Nebari homeworld culture is conveyed in "A Clockwork Nebari."
Farscape Wiki http://farscape.wikia.com/wiki/Nebari