There are many red wiggler facts that you become aware of along the way when you start worm composting. One of these facts, and it applies to earthworms as well (it actually easier to see on earthworms…think back to the last time you went fishing and were using them as bait), is knowing that worms are hermaphrodites. This doesn’t mean that they can breed without a mate like most people think. It means that they have the sexual organs of both male and female. So when looking for a mate they don’t have to look for a worm of the opposite sex. Any worm of mating age will do the trick. This is part of the reason that the population in your wormery increases so quickly!
So clitellum is the sexual organ that all worms have. According to Wikipedia it is defined the following way:
The clitellum is a thickened glandular section of the body wall in earthworms and leeches, that secretes a viscid sac in which the eggs are deposited. It is present about 2 centimetres (0.79 in) behind the anterior end of the body (around 14th, 15th and 16th segments).
A clitellum is part of the reproductive system of clitellates, a subgroup of annelids which contains oligochaetes (earthworms) and hirudineans (leeches). The clitellum is a thick, saddle-like, ring found in the epidermis (skin) of the worm, usually with a light colored pigment. To form a cocoon for its eggs, the clitellum secretes a viscous fluid. This organ is used in sexual reproduction of some annelids. The clitellum becomes apparent in mature annelids but may be hard to locate visually in younger annelids. In leeches, it appears seasonally. Its color is usually slightly lighter than that of the body of the annelid. Occasionally, living segments of the worm will be shed with the clitellum.
So the Clitellum is a very important part of breeding when it comes to your wormery. For both the red wiggler and earthworm, depending on what breed of worm you keep.