Compost-ology Worm Cocoon Formation
Worm Reproduction & Development

Reproduction dictates survival of a species. Organisms like worms which provide food for many others, must reproduce ample offspring to offset predation. Red wiggler reproductive methods, while simple, are very effective.

Most worms are hermaphrodites, meaning each one is both male and female. While worms possess both male and female sexual organs, a red wiggler cannot produce offspring alone. Red wigglers must join for successful mating and reproduction to occur.

Some species of worms are parthenogenic, meaning that they can produce offspring without cross-fertilization. Red wigglers are hermaphroditic but not parthenogenic.

When a red wiggler is sexually immature its body segments are uniform throughout its entire length. As it matures it develops a bulbous gland about one-third of the way down its body called the clitellum. It looks like a swollen band around the body, thus the popular term, bandling worms. The clitellum produces mucus needed for cocoon production.

Two worms come together at the clitellum and use their hair-like setae to hold fast to each other. While joined they exchange seminal fluid. At the same time, grooves on the underside of the worm help transport the seminal fluid to the seminal vesicles for later use. Each worm begins to secrete a mucus ring around itself.

After being joined for up to three hours, the worms separate. The mucus on each worm begins to harden as the worm starts to back out of, or slough off, this ring. During this process seminal fluid, ovum and amniotic fluid are deposited into the mucus ring. As the ring passes over the worm's head it seals, forming the lemon-shaped, yellow-colored cocoon. Over a period of weeks, the cocoon hardens to a beautiful ruby red as hatchlings mature.

Under favorable conditions your red wiggler worm population will multiply rapidly. A mature red wiggler (3 months old) can produce two to three cocoons per week. Each cocoon averages three hatchlings. Cocoons take up to 11 weeks to mature and hatch. Hatchlings require two to three months before they grow to be mature breeding worms.

Population productivity over 11 week incubation period:
1 worm x 3 cocoons/wk x 3 hatchlings/cocoon = 9 hatchlings/wk
11 weeks x 9 hatchlings/wk = 99 hatchlings/worms

In two to three months those hatchlings will be mature breeders, producing offspring of their own. At the same time, their parents are continuing to mate and create offspring.

As conditions in the bin become crowded, the adult worms will try to leave the bin rather than compete with the young for food. Population increase is a good reason to harvest the bin every four to six months.

A cocoon is the small, yellow, lemon-shaped object that is produced by red wiggler mating. According to C.A. Edwards and P.J. Bohlen in Biology and Ecology of Earthworms, red wigglers can produce as many as 198 cocoons per year.

Gestation occurs over a period of 11 weeks. The cocoon is hardened mucus and, like a bird egg, contains all the necessary nutrients for the development of the hatchlings. Each cocoon contains between two and twenty potential hatchlings. On average, three will emerge.

Climate conditions directly offset cocoon production; for example, when there is too little moisture, the worms will cease reproduction. Peak production occurs when ambient ground and air temperatures are between 65º-85ºF (18º-27ºC) and the environmental moisture content within the bin is between 80-90%. That means moist to the touch but not dripping (like a wrung-out sponge).

When environmental conditions are not appropriate for survival, the cocoons will lie dormant awaiting more favorable conditions. Cocoons have been known to survive for up to three years under extremely dry conditions without being adversely affected.

It takes five to 11 weeks for the cocoon to mature and hatch. The newly hatched worms first appear as tiny white, thread-like creatures. In approximately eight hours they gain their hemoglobin and change color from white to pale pink to brick red.

Depending on bin conditions, temperature and moisture, hatchlings can take from 53 to 75 days to become sexually mature — two to two and one-half months. The complete generational cycle from one adult worm to the next is anywhere from three to five months.

Adolescence is a short lived phase for red wigglers. The length of the worm increases almost daily as their principal function during this phase is to eat, eat, eat!

Like many creatures, sexual maturity in red wigglers is delayed by cold weather, but not growth rate. Lobsters raised in cold water compared to warm water are a good example. Those raised in cold water grow fairly large before they become sexually mature, while warm water lobstrs are smaller upon reaching maturity.

Juvenile worms are distinguishable from adult worms because they look the same from head to tail and do not have the band indicating the clitellum. They are the same color as adults and may be just as large.

Red wigglers spend an average of 56 to 72 days or about 8 to 11 weeks in this development stage.

Adult red wigglers are characterized by the formation of their bulbous clitellum. The presence of the clitellum means they are sexually mature.

Diet plays a key role in the worm's size, which may vary from four to seven inches. Smaller size does not mean that something is wrong, but smaller worms produce smaller cocoons and fewer offspring.

There is no conclusive evidence that gives a definitive life expectancy for worms. However, a well cared for herd in your bin may give you sterling service for five years or more.