Note 5 — Chapter III · CAUSES OF VARIATION.

The great preponderance of the phytophagous over the predacious tribes, in the hotter regions of the earth, is a remarkable fact, and strongly suggestive of the relation which the insect and vegetable worlds (both of which attain their maximum in those zones) bear to each other. "The carnivorous beetles, or Carabidæ," says Mr. Darwin, "appear in extremely few numbers within the tropics. The carrion-feeders and Brachelytra are very uncommon; on the other hand, the Rhynchophora and Chrysomelidæ, all of which depend on the vegetable world for subsistence, are present in astonishing numbers. The orders Orthoptera and Hemiptera are peculiarly numerous; as is, likewise, the stinging division of the Hymenoptera, the bees, perhaps, being excepted."—Journal of Researches, p. 34.