the first female weyrleader and the first female rider of a blue dragon. Green dragons are the smallest normal color (20–24 feet or meters long), and make up about half of all dragons on Pern (fifty percent). They are female, but unlike the queens, they are infertile—due to the chronic use of firestone—and can produce flame. They are extremely valuable in Threadfall because of their agility, but they lack the stamina to last an entire Fall and generally fly in two or three shifts. Originally, greens Impressed only girls; however, after various natural disasters and plagues decimated Pern's population, women were needed to help repopulate the planet. Since going between during pregnancy can induce miscarriage and because removing pregnant riders from the Wings reduced the effectiveness of the Wings, it became impractical to present large numbers of women as candidates for Impression. Thus, green dragons began Impressing homosexual boys; by the time of the end of the Second Pass, female green riders were becoming rare. By the time of Moreta in the Sixth Pass, female green riders were entirely forgotten, although greens gradually begin Impressing to women again in the Ninth Pass. Females of any sexual orientation may Impress green. There is only one white dragon mentioned anywhere in the Pern novels: Ruth, whose rider is Lord Jaxom of Ruatha Hold. He is not an albino, as his hide contains very faint patches of all the normal dragon colors. Ruth's egg would not have hatched if Jaxom had not forced it open and released the dragonet from a thick membrane sac; thus, it seems likely that white coloration in dragons is normally a lethal mutation. Although his parents are the largest queen, Ramoth, and largest bronze, Mnementh, in the history of Pern, Ruth is smaller than even a normal green dragon in his time; he is only slightly larger than the largest dragons of the first generation. While his exact length is never specifically mentioned in the books, it does state that he stands higher than a runnerbeast (horse) at the shoulder, extrapolations suggest that he might be 18 feet or meters long. He is male or neuter (undetermined), and assumed sterile, with no urge to mate. Ruth also has the unusual ability to intuitively orient himself in time. The larger a color is, the less common it is. For instance, there are more blues than browns, and there are