Read it through once

The world of plants supports all animal life, from the mite to the elephant. There are most intricate relations between one form of life and another. Thus a Rose tree attacked by an aphis or green-fly may be succoured by the slim ichneumon, or other thin-waisted fly, which lays its egg in that of the aphis. Another insect, say a spider, catches the ichneumon. A starling may eat the spider, and be itself eaten by an owl.