Chapter 5

Using the Right Kind of Worms

Most people think that “a worm is a worm is a worm.” In fact, there are many kinds of worms, each with different jobs to do. It is important to use the right worms in your home vermicomposting system.

Most of the worms that you could dig up from your garden would not be suitable for vermicomposting. You want a worm that processes large amounts of organic material. The worms should reproduce quickly in confinement and tolerate the disturbance caused when you lift the lid to bury food waste or add bedding. When small organisms are raised in a controlled environment, they are said to be cultured; the culture of earthworms is known as vermiculture.

Types of Worms

The soil-dwelling species of worm, or “earthworkers,” don’t process large amounts of organic material like the “composters.” They don’t reproduce well in confinement, and they won’t thrive in a worm bin if you dig around and mess up their burrow system. Understanding the characteristics of different worms and why common names can be confusing is the purpose of this chapter.

Redworms are the most satisfactory kind to use in your home vermicomposting system, but what I call “redworm” you may know as “red wiggler.” Your neighbor may call it a manure worm. The bait dealer down the road may refer to it as a red hybrid. Other common names for this same animal are fish worm, dung worm, fecal worm, English red worm, striped worm, stink worm, brandling, and apple pomace worm. A distinct pattern of alternating red and buff stripes characterizes some of these worms, hence another common name, tiger worm. Calling earthworms by common names can cause communication problems. With so many names, how can any of us know when we are talking about the same worm?

All earthworms belong to one of three groups, depending on their behavior in their natural environment.

Epigeic (Greek for “upon the earth”) worms are commonly called composters. They live and feed in surface mulch areas on decaying matter. These worms are usually small, reproduce rapidly, and, because they have pigmentation, are reddish brown in color. They do not burrow and are the type of worm used in vermicomposting. Some scientists further divide this group into those worms that live mostly in compost, such as Eisenia fetida, and those that live on the surface of soil in leaf litter, such as Lumbricus rubellus.

Endogeic (Greek for “within the earth”) worms live in the topsoil. Ranging in size from small to large, these worms lack pigmentation. They will appear to be blue-gray, yellow, pink, or a whitish color. These worms feed on soil and decaying organic matter and form a network of horizontal burrows.

AneCic (Greek for “out of the earth”) worms live in the subsoil, making vertical burrows as deep as 6 feet. These large worms feed on fresh surface litter that they drag down into their burrows. They deposit their waste (castings) at the surface. Like epigeic species, they also have pigmentation, causing them to be reddish brown in color.

What’s in a Name?

A marketing strategy for some worm growers is to create a name that establishes their worms as unique or better than others so the growers can justify a higher price. Such names as Jumbo Worm or Super Giant come to mind. These are probably not different species, and certainly not hybrids (combinations of species), but are simply likely to be well-fed worms. If you are just buying some worms for fishing, it probably doesn’t matter. Superworm is the common name for the larvae of the darkling beetle and is sold as pet food for reptiles. Zophobas morio is the scientific name.

But if you are going to use the worms you buy to set up a worm composting system, make sure the grower can give you the scientific name. That way you can be sure that the worm you purchase is suitable for composting and not an invasive. And if you need to learn more about it, you can read some of the scientific papers about your worm of choice.

Scientific Names

To be certain they are talking about the same thing, scientists have developed a precise system for naming organisms. Since much information in this book comes from scientific papers, I will be using scientific names. So that you won’t be confused when I do, here are some basic rules that all scientists follow:

The International Commission on Zoological Nomenclature provides and regulates a uniform system of zoological nomenclature (a system of names), ensuring that every animal has a unique and universally accepted scientific name. As more research is done on a species, it is possible that not only the species name can change but in some cases the genus can change. An excellent website to research earthworm names is DriloBASE Taxo. The contributors include scientists who are well known in the vermicomposting community, and the site lists synonyms to clarify the names of the worms being researched (see Resources.).

Composting Worms

Certain epigeic worms can eat and digest organic material quickly. Although they have a short life cycle, their reproductive rate is high. Additionally, they tolerate handling and a wide range of environmental factors. Although there are thousands of species of worms, only a few have been used extensively in vermicomposting. Let’s examine those now.

Illustrations of soil layers showing how anecic vs. endogeic worms live and work.

Endogeic worms live and work on the surface in upper organic layers of topsoil. The soil-dwelling anecic worms move from one layer to another, mixing layers as they go.

Temperate Species

Redworm

Eisenia fetida

The worms I use are Eisenia fetida (which I pronounce as “i-SEE-nee-uh FET-id-uh”), said to give off a fetid odor when roughly handled. The other common names for this worm are brandling or tiger worm. It has a red-buff transverse segmented stripe. These worms process large amounts of organic material in their natural habitats of manure, compost piles, or decaying leaves. They are fast reproducers and tolerate a wide range of temperatures, acidity, and moisture conditions. They are tough worms and withstand handling well. Because sufficient markets exist encouraging people to culture E. fetida on a part- or full-time basis, anyone may purchase them almost any season of the year. They can readily be shipped via package delivery services or through the mail. Many people who vermicompost would like to transfer extra worms from their bins to their gardens to increase the worm populations there, but I never recommend this for E. fetida because they are not soil dwellers.

Redworm

Red Tiger

Eisenia andrei

Eisenia andrei is a relative that lacks the red and buff striping of the redworm. Known as the red tiger, E. andrei (abbreviating the genus name to just its initial saves space once it has already been spelled out in full) has slightly better performance characteristics then E. fetida. Many times this species is incorrectly called E. fetida. It has been determined that E. fetida and E. andrei are two different species; however, they are easily confused with one another. Although DNA barcoding tests can prove that E. fetida is E. fetida, the same test will sometimes identify E. andrei as E. fetida. Most commercial cultures contain a mixture of both species, and growers do not separate them.

Tropical Species

Indian Blue Worm

Perionyx excavatus

Perionyx excavatus is suitable for vermicomposting in warm climates. Called the Indian blue worm in some regions, it is a tropical species that reproduces well in culture and tolerates handling. Scientific investigations show that P. excavatus is intolerant of cold, so it would not live outside through the winter in a cold climate. It also has a tendency to move out of worm bins for no apparent reason, a characteristic my staff acknowledges by calling them “travelers.”

Indian Blue Worm

African Nightcrawler

Eudrilus eugeniae

Another restless worm used for vermicomposting, Eudrilus eugeniae is large and commonly known as the African nightcrawler. As its common name suggests, this species has a tropical origin. The worms can reproduce quickly and process large amounts of organic material rapidly within their optimal temperature range of 59 to 77°F (15 to 25°C); temperatures below 50°F (10°C) kill them. E. eugeniae is therefore limited to warm climates or heated buildings.

African Nightcrawler

Invasive Worms

Invasive species are those that are nonnative to an ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

Eleven thousand years ago, northern North America was covered in ice. This glaciation destroyed native worms. The forests in that part of the world evolved without earthworms. With the arrival of European settlers in the 1800s, earthworms began to enter North America again. Since that time, they have continued to be distributed and spread through soil redistribution, in plant pots, after being used as bait, and via mud on vehicles and boots. On their own, worms move slowly. Their rate of movement has been calculated at less than 30 feet per year. It would take an earthworm over a thousand years to move just over 5 miles! It is people who brought earthworms to northern North America.

About three decades ago, scientists in Minnesota and New York noticed that the forest floors were changing. Since then, studies have shown that some worms can have a negative impact on ground-nesting birds and forest regeneration and increase the spread of invasive plants such as garlic mustard.

Asian Jumping Worms

Genus Amynthus

Jumping worms are sold for bait and as a composting worm. Common names include Alabama, Georgia, Jersey, or Asian jumpers. Some call this a snake worm or crazy worm because they move like a snake when picked up. This worm can eat and process more than its body weight in organic material each day. They tend to process leaves and soil until the soil becomes dry and granular. Originating from Southeast Asia, the worms are a problem in many parts of North America. These worms were found in 75 percent of the test plots studied in the Great Smoky Mountains National Park. The park now has a regulation that no live bait can be used for fishing within its boundaries. Earlier in 2009, all 51 species of this genus were listed by the state of Wisconsin as prohibited species, a designation made to keep the worms from coming into the state. When the Wisconsin Department of Natural Resources discovered jumping worms in the state in 2013, their designation was reclassified as “restricted species.” Neither prohibited nor restricted species may be sold, introduced, transported, or propagated in Wisconsin.

Asian Jumping Worm

Red Earthworm

Lumbricus rubellus

At one time, Lumbricus rubellus was considered suitable for worm composting. Some consider L. rubellus to be the “true” redworm; others call it the dung worm or the red marsh worm. It has been found in compost heaps and manure piles, and in pastures, particularly under cow patties or manure. Some worm growers claim to have L. rubellus in their beds, but scientists consistently report that every time they have checked those claims, the worms have been E. fetida, E. andrei, or a mixture of both species. Studies regarding the maturation and reproductive rate of this worm have shown it to be less than ideal as a vermicomposter. L. rubellus looks similar to a nightcrawler but is smaller. The top anterior of the worm is purple-maroon, and it is lighter at the tail and underneath. It tends to be thicker-bodied between the clitellum (the region that secretes cocoon material) and the head than other worms. It is commonly sold as fish bait. Because it feeds in the litter layer and in the top few inches of soil, it is sometimes referred to as an epi-endogeic species. Great Lakes Worm Watch lists this worm as problematic in their forest, as it can rapidly degrade and remove the forest floor.

Red Earthworm

How to Prevent the Spread of Invasive Worms

In 1881, Charles Darwin published The Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits. This book showed us how remarkable earthworms are. They are amazing creatures that can increase soil fertility and aerate soil with their movement. Those of us who are worm workers know and appreciate what benefits earthworms provide, but even a good organism can become an invasive when it is not handled with care.

What do we as worm workers do to stop an invasive species? First of all, I only recommend Eisenia fetida or E. andrei for home composting. Since these worms feed on the top layer of the soil, they do not survive winters. Second, I recommend following the directions of national and state agencies regarding these worms. These directions usually include the following:

Other Worms in North America

If you dig up your garden, you will mostly likely find species of worms other than those described in this chapter (aside from Lumbricus terrestris, below). In the northern United States and southern parts of Canada, about 90 percent of the worms would be one of eight soil-dwelling species, including Aporrectodea caliginosa, A. trapezoides, A. tuberculata, Dendrobaena octaedra, Dendrodrilus rubidus, L. terrestris, L. rubellus, and Octolasion tyrtaeum. More species will be found in the southern part of the United States, which was not covered by glaciers 11,000 years ago.

Identifying these species would require suitable magnification, a good pair of forceps, and a tool for pointing or probing. Depending on the guide or identification key you use, preliminary determinations of species can be made on the basis of pigmentation, general body shape, length of the worm, and position of the clitellum. You may have to identify the type of projection over the mouth, locate the position of various openings for sexual organs, and determine the pattern for setae (bristles) on each segment. We need more people who can identify kinds of worms. I encourage you to learn how to do so.

Canadian Nightcrawler

Lumbricus terrestris

Today more than 5,000 species of earthworms have been classified, and of those, Lumbricus terrestris was the first. Commonly called the Canadian nightcrawler, these worms are widespread in Europe and North America and are found in parts of New Zealand and Australia. Most people recognize the nightcrawler, and it has been called many names, including the dew worm, night walker, rain worm, angle worm, orchard worm, and night lion.

Nightcrawlers are not suitable worms for the type of home vermicomposting system described in this book. I once placed 80 nightcrawlers in my worm bin along with the redworms already there. Two months later, I found only one live nightcrawler, and it was immature. Although satisfactory environments can be created for nightcrawlers indoors, they require large amounts of soil, and the bed temperature cannot exceed 50°F (10°C). For obvious reasons, those conditions are very impractical for a home vermicompost bin. Nightcrawlers dig burrows and don’t like to have their burrows disturbed. If you try to bury food waste, nightcrawlers move quickly around the surface of the box trying to escape your digging.

Nightcrawlers do, however, play important roles in soil fertility in some ecosystems. These large soil-dwelling earthworms have extensive burrows extending from the ground surface to several feet deep. They come to the surface on moist spring and fall nights and forage for food, drawing dead leaves, grass, and other organic material into their burrows, where they feed upon it at a later time. Nightcrawlers perform important soil-mixing functions. They take organic material into the deeper layers of the soil, mix it with subsoils that they consume in their burrowing activities, and bring mineral subsoils to the surface when they deposit their casts. Through their burrows, nightcrawlers also aid in soil aeration and in water retention by increasing the rate at which water can penetrate the deeper soil layers. They may not be good for your worm boxes, but they are very good for your gardens. They are, however, not good for the northern deciduous forests, as they degrade the forest floor and can enable the spread of invasive plants in some regions.

Canadian Nightcrawler