Skip to main content

Compost Guide | Organisms and Composting

Compost Guide

Organisms & Composting

Revised On: Nov. 25, 2023 - 8:20 a.m.

Worms and insects are fairly standard occupants of outdoor (and sometimes indoor) piles. Organisms that feed on compost piles can be classified into primary, secondary and tertiary consumers.

Primary Consumers

These eat organic residue in a compost pile and are key to the composting process. In addition to breaking down the material, larger primary consumers help aerate the compost. Microbes and decomposers (fungi, mites, worms, millipedes, pill bugs, slugs, etc.) fall into this category.

Secondary Consumers

These eat the primary consumers and typically do not consume organic residue. But they help regulate the number of primary consumers in the pile and aid in releasing nutrients back into the compost. Springtails, nematodes, protozoa, soil flatworms, mites and feather-winged beetles fall into this category.

Tertiary Consumers

While some tertiary consumers are considered harmful or counterproductive to the pile, a small amount of these can help regulate secondary consumers by eating them.  Centipedes, rove beetles, carabid beetles, ants and some mites fall into this category.  

Beneficial Insects

The following aid bacteria in decomposing food scraps, and some, like worms, also produce castings that increase the nutrient value of your compost.

  • Isopods (aka roly polies, pill bugs, woodlice)
  • Black soldier fly and their larvae
  • Millipedes
  • Worms, slugs, and snails


The following are indicators of an imbalance in your pile and others prey on beneficial insects | Troubleshooting Pests >

  • Fruit and house flies
  • Rove beetles
  • Centipedes
  • Ants
  • Earthworm Mites