Many kinds of small animals live on the stems and leaves of park plants. Most of these small animals are insects. Insects are small, six-legged invertebrates. They include butterflies, beetles, flies, bees and grasshoppers. 

Insects gain their energy either by eating plant parts or other insects. They play an important role in the park's food chain.

The food chain begins at the level of the producer. Usually, the producer of a food chain is a green plant that creates sugar from sunlight during photosynthesis. Many kinds of insect larvae eat plant leaves. When this happens, the energy produced by the plant is consumed by the larvae. Other insects or animals can then eat the larvae, gaining the energy contained in it. These animals can serve as the source of food for even larger animals. All of these animals are consumers. Unlike plants, they cannot produce the energy they need by themselves, but instead have to use other organisms as their food. 

When animals and plants die, their parts are broken down by decomposers. Decomposers can be bacteria, insects or other invertebrates that use parts of dead organisms as their energy source. When the decomposers break down dead organisms, the nutrients and compounds contained in their bodies are released back to the environment. Plants use these materials to grow and photosynthesize. When this happens, the food chain begins once again at the level of the producer.

Picture: A moth larva eating the leaves of a plant.