The breakdown of detritus into small particles by earthworms is called:

The breakdown of complex organic matter into inorganic substances such as carbon dioxide, water, and nutrients by decomposers is called decomposition. Dead plant remains such as leaves, bark, flowers, and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification, and mineralisation. Detritivores, such as earthworms, break down detritus into smaller particles. This process is called fragmentation. The earthworm is often referred to as the farmer's friend. This is so because they help in the breakdown of complex organic matter as well as in the loosening of the soil.