There are approximately 2,700 species of different earthworms across the world. They commonly live in habitats that us humans would find less than desirable; deep within the soil. However, you’ve definitely noticed a worm crawling along on the surface at night or after a shower in the spring or fall. And, you may have even come across two worms mating when the conditions are ideal, like when it’s under 50 degrees. While the whole idea or worms reproducing sounds a bit gross for some people, the lifecycle of a worm is actually fascinating. Why else would Darwin devote 39 years to study the earthworm? There’s a lot to learn from our slimy neighbors.
Even with the differences between all of the varying earthworm species, they each have similar life cycles. For instance…
Did you know that earthworms have both male and female sexual organs? Sure you did. But, how do they reproduce? These hermaphrodites must first find a mate, which can begin as soon as that wide, whitish band towards the head called the clitellum forms at about four to six weeks old. The clitellum is important for reproduction because this where the reproductive organs exist.
Unlike humans, worms aren’t looking for a companion. They just stumble upon each other. However, once two worms have found each other, they’re ready to mate. They will join together in opposite directions as they line up their clitellums. Once the worms are lined up, the clitellum will produce a mucous sheath and nutritive materials. As the sheath slides forward, it will pick up ova from the earthworm’s ovaries, as well as packets of sperm that will be stored in sacs. Once the clitellum sheath slides off the worm’s head, the ends are dried and sealed to form the cocoon located on each of the worm’s clitellum’s.
Inside the cocoon the sperm fertilizes the eggs and worm embryos will grow. It’s similar to the process of a chick developing inside of an egg.
In the beginning, the cocoon is soft. However, once it has been buried deep within the soil it will become slightly amber and leather-like. Eventually, the cocoon will develop a resistance to drying and damage. As for as its size, cocoons are incredibly small and have the shape of a lemon. They can survive underground until conditions are right for hatching with each cocoon containing one to twenty fertilized ova or eggs.
Once the embryos have consumed nutritive material, they fill the cocoon and are all set to hatch out one end. This usually occurs within three weeks to five months depending on the gestation period of the species as well as the temperature and soil conditions – it has to be dry. If conditions are not right, the hatching can be delayed until the spring – but they can survive for years if need be. This, however, causes the cocoons to overwinter in the soil.
Despite the possibility of a cocoon holding up to 20 juvenile earthworms, only a few will emerge. The baby worms look just like adults of their species, except that they are only about a half an inch long and are white in color. They are not nurtured by their parents and will begin to eat immediately once out of the cocoon. In fact, a worm can eat their weight each day.
It usually takes between 10 and 55 weeks for baby worms to mature into their full adult size.
The Circle of Life
Once earthworms have reached adulthood – which can can be at four to six weeks – they’re mature enough to reproduce and the cycle begins all over. Worms can produce anywhere between 3 and 80 cocoons each year and can continue to produce cocoons as long as their is a sperm supply. However, the species who reside deeper underground will produce less since they’re protected and can hatch without disturbance. Species that live closer to the surface will produce more cocoons.
Worms can live for years, usually anywhere between 4 to 8 years. It all depends on the climate and predators like birds, toads or rats. However, since the body of a worm consists of 90% water, one of the most common causes of death is when the worm’s skin dries out.