The third phase of animals and plants is destruction (destructio). This includes how plants and animals live off each other in an unbroken chain:
plant => aphid => hover fly => robber fly => dragonfly => spider => sparrow => hawk
This is an example of a food chain, but Linnaeus did not attempt to describe food webs that include mutualism, decomposition, and the fact many species feed on several trophic levels.
Cycles in nature
The final phase of destruction is how dead organisms decompose down and give rise to mush. In the first step, the scavengers are absolutely necessary for the cycle: The whole earth would be piled up with carcasses and stinking bodies if some animals did not consider them delicacies. Linnaeus emphasizes the importance of earthworms in the same way, but of course every farmer in the 18th century knew all this. How the further transformation into decomposed soil takes place was difficult to understand in the 18th century, but Linnaeus in at least explains that fungi are involved in the decomposition of e.g. a dead tree.