For most types, some mechanism stimulates the worm to produce a cocoon which is deposited into the soil. One or more live worms eventually emerge from the cocoon. They reach sexual maturity in 3-6 weeks. Some species can regenerate amputated body parts but no know species, if cut in two, can generate two viable worms. In addition to recycling organic matter for plants, earthworms, by their borrowing action and the deposition of castings, modify the soil structure and help to improve such properties as aeration, moisture retention, and water infiltration.
Some gardeners complain that because earthworms eat organic matter they cause the soil to harden.
It is true that the organic matter is somewhat depleted by earthworms, but earthworm activity reduces, rather than increases, soil compaction. If soil hardening is a problem, it can be easily remedied by adding organic matter. With proper water and composting and with the assistance of earthworms, our garden soils can be maintained in a healthy, productive state.