Earthworms: Oligochaeta

Earthworms defend themselves in a variety of ways. Those living in tunnels escape danger by quickly withdrawing into their burrows. Those living near or on the surface have the ability to move quickly. They jump and thrash wildly about and will even purposely break off a few tail segments when threatened by a predator. Species living deep in the soil have few defensive behaviors. Some will twist and coil their bodies or produce bad smelling or tasting fluids.

Earthworms have both male and female reproductive organs. Individuals in cooler climates mate in spring or fall to exchange sperm. Many tropical species are active during the rainy season. Worms align themselves in opposite directions and place sperm directly into the other's body. The collarlike cocoon produced by the clitellum passes over the female reproductive openings to receive one or more eggs, and then over the male openings to receive sperm. Fertilization takes place inside the cocoon.

Cocoons are deposited in the soil soon after mating. The developing eggs are nourished inside the case with materials also produced by the clitellum. The young earthworm passes through several stages before emerging from the cocoon as a small earthworm. Depending on the species, young earthworms may take several months or years to reach adulthood.