. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. X. Orthoptera. 2S5 " of dome over the wing-covers, and which has probably the " effect of increasing the ;37. Kg. 13. Chloroccelus Xanana (from Bates), a, b. Lobes of opposite wing-covers. We thus see that the musical apparatus is more differentiated or specialised in the Locustidaa (which include, I believe, the most powerful performers in the Order), than in the Achetidse, in which both wing-covers have the same structure and the same
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. X. Orthoptera. 2S5 " of dome over the wing-covers, and which has probably the " effect of increasing the ;37. Kg. 13. Chloroccelus Xanana (from Bates), a, b. Lobes of opposite wing-covers. We thus see that the musical apparatus is more differentiated or specialised in the Locustidaa (which include, I believe, the most powerful performers in the Order), than in the Achetidse, in which both wing-covers have the same structure and the same Landois, however, detected in one of the Locustidre, namely in Decticus, a short and narrow row of small teeth, mere rudiments, on the inferior surface of the right wing- cover, which underlies the other and is never used as the bow. I observed the same rudimentary structure on the under side of the right wing-cover in Phasgonura viridissima. Hence we may infer with confidence that the Locustida; are descended from a form, in which, as in the existing AchetidaB, both wing-covers had serrated nervures on the under surface, and could be indifferently used as the bow ; but that in the Locustidse the two wing-covers gradually became differentiated and perfected, 27 Westvvood, 'Modern Class, of Insects,' vol. i. p. 453. 38 Landois, ' Zeitsch. f. wiss. Zoolog.' B. xvii. 1867, s. 121, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York, Appleton
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