The term “Tailies” represents the survivors who sat in the rear section of Oceanic Flight 815, it was originally coined by Hurley in Fire + Water. The tail section tore off and crashed on the western side of the Island, unlike the middle section, which crashed farther south. They initially included 22 people but were unknowingly joined by a spy from the Others only moments after the crash, so they thought they numbered 23. Ana Lucia took lead of this group of survivors.
On the Island
On their first night on the Island, three of the tailies were taken by an attack party of the Others. At the same time, two of the Others were killed by the tailies. The tailies decided to remain on the beach to keep a signal fire burning for possible rescue parties. Four of the tail-enders died of their injuries in the subsequent days. Two weeks after the crash, the Others struck again and nine more were taken, including the children, Emma and Zach. Two adults of these nine later joined the Others, as is apparent by their later appearance as part of the Others background (#8 and #9). One of the Others was also killed. They then decided to move into the jungle.
On the 15th day, after the tailies had traveled for three days, they made camp next to a small stream. Nathan was held prisoner in a makeshift pit and starved by Ana Lucia, who believed he was the spy. After Ana Lucia threatened to start cutting his fingers off, he was freed by Goodwin who broke his neck after he escaped from the pit. After the disappearance of Nathan, the tailenders started moving again.
On the 27th day the tailenders discovered, and moved into, the abandoned DHARMA Initiative station, the Arrow. In a box they discovered a radio. Goodwin, accompanied by Ana Lucia, took this radio to higher ground to get a signal. However in the meantime Ana Lucia confronted Goodwin, killing him in the struggle that followed. According to Ben, Goodwin liked Ana Lucia and advocated that she be considered “worthy” (presumably of becoming an Other).
On the 45th day, the tailenders captured Sawyer, Michael and Jin (mistaking them for Others) when these three washed up on shore. They first held the captives in the pit and then brought them to the Arrow station.
When the existence of the main survivor’s group was revealed, the tailies decided to trek across the Island, staying close to the shoreline and carrying a wounded Sawyer. Shortly before arriving at the main camp, Cindy disappeared, and in the confusion Ana Lucia accidentally shot and killed Shannon.
In the end, when the tail-end and the middle section survivors were reunited, only four tailies remained: Ana Lucia, Mr. Eko, Libby, and Bernard. After the murders of Ana Lucia and Libby, and Eko’s death in “The Cost of Living”, Bernard remains the only tail section survivor that is neither dead nor captured (and was in fact only in the tail section to use the restroom). Five of the “taken” tailenders joined the Others: Cindy, Emma, Zach, and two tailies background (#08 and #09).