230 Charles Darwin. 



that I can only make reference, at this time, to a few 

 of the most important and striking of them. 



He pointed out the great preponderance of phy- 

 tophagous over predaceous species in the tropics as 

 exemplifying the relation of the insect and plant 

 worlds, both of which attain their maximum in those 

 zones. CarabidcB are few ; Scavengers and Brachely- 

 tra very common ; Rhynchophora and Chrysomelidce 

 astonishingly numerous. (" Journal of Researches," 

 etc., p. 34.) 



He showed by minute observations that the insect 

 faunas of Tierra del Fuego, separated from Patago- 

 nia only by the Straits of Magellan, have nothing in 

 common, and he discussed the influence of primary 

 barriers on the distribution of species, as shown in 

 the marked divergence of the faunas on the eastern 

 and western slopes of the Cordillera. " We ought 

 not," he remarks, " to expect any closer similarity 

 between the organic beings on the opposite sides of 

 great mountain ranges than on the opposite shores of 

 the ocean, except for species which have been able to 

 cross the barrier, whether of rock or salt water.' 

 {Ibid., pp. 326, 327.) 



I believe he was the first to draw attention to the 

 paucity of insects on islands, and to establish the 

 principle that the smaller the area, the less favourable 

 it is for the development of insect life. {^Ibid., p. 391.) 



It is a fact of observation that islands predispose 

 to the apterous condition among insects, a fact that 

 is especially noticeable in Kerguelen's Land, as ob- 

 served by Dr. Hooker, and particularly by our fellow 

 member, Dr. Kidder. Darwin (" Origin of Species/ 



