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Adults And Young: Within 40 to 85 days, depending on the species, the young develop sufficiently to begin flying. While the young learn to fly, the flight feathers and other plumage of the adults and young undergo their yearly renewal. By the time the brood is two or three months old, both the youngsters and the adults and young are ready to migrate to winter quarters.
The shell of most turtles is marked with interesting colors and gay patterns. In some species the color and pattern may occur also on the head and neck of the animal. With the exception of a few species, the young of turtles are much more brightly marked than the adults and young. There is extreme variation in the markings of young turtles, even among the same species, and few of them resemble the adults and young.
The behavior of the Burkitt virus resembles that of poliomyelitis virus: it is very widespread and causes few or no distinctive symptoms when it infects children, but it may cause a ,recognizable disease in adults and young. Moreover, its spread is more rapid under conditions of poor sanitation; hence populations with high economic standards and good sanitation facilities have a high proportion of susceptible adults and young who in childhood did not become infected and thereby immunized against the virus. The prevalence of infectious mononucleosis among young adults and young is thus explained.
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