A ladybird feeding beside an aphid colony connects three things: the plant, an insect taking its sap and an insect eating that feeder. A bird may take caterpillars from the same plant. These overlapping feeding relationships form a food web.

The diagram shows a few possible links, not a fixed pyramid of population sizes. Different animals eat different foods, and diets can change with life stage. Many adult hoverflies visit flowers while their larvae eat aphids; other hoverfly larvae have different diets.

Wildlife has value beyond its usefulness to your plants. Providing habitat can also support pollination, decomposition and some natural pest control. It cannot promise an undamaged crop or a garden that maintains itself.