Note 1 — Chapter VI
Reading edition
For the evidence see Tutt, J. W., Trans. Ent. Soc., 1898, p. 17. Compare the remarkable case given by Gulick (Evolution Racial and Habitudinal, p. 123) of the two races of Cicada, which are separated by reason of their life-cycles, one having a period of 13, the other 17 years.