The Real Dirt on Composting Worms

November 11, 2025

Most people naturally associate the word “earthworm” with the slimy, wiggling creatures they find in their gardens or out on the driveway/sidewalk after a heavy rain.

They live in soil.
They come in a variety of (usually dull brownish/grayish) shades, and a variety of sizes.
They are good for fishing.
They are good for the soil.
They are basically all the same.

End of story.

Or is it?

In this article - another installment in our ongoing critter series - we’re going to dig deeper and look at some of the misconceptions surrounding earthworms, especially as they relate to the group we refer to as the “composting worms”.

Taxonomic & Ecological Classification of Earthworms

Phylum: Annelida
Subclass: Oligochaeta
Suborder: Lumbricina

The term “earthworm” refers to the terrestrial invertebrates in the phylum Annelida, subclass Oligochaeta, suborder Lumbricina. Most of them do indeed live in some form of soil-based habitat, but - as I’m sure you can guess already - this isn’t always the case.

Which brings us to the (very helpful) ecological classification of these organisms!

There are 3 major ecological groupings of earthworms based on where they live in the soil profile. This alone should help us to shed a lot more light on why “composting worms” are so darn good at what they do, and why most of the common “wild” earthworms aren’t nearly as ideal a choice for vermicomposting.

Anecic Worms

These are the deep burrowing worms. They create tunnels that can extend quite far down into the soil profile, with a primarily vertical orientation. They tend to be larger worms that live a relatively solitary life. Prime examples include the large “nightcrawlers” (e.g. Lumbricus terrestris - a.k.a “Dew Worms” / “Canadian Nightcrawlers”) you find on your lawn or out on the sidewalk after heavy rains, or buy at the tackle shop for fishing.

Anecic worms also tend to be quite intolerant of warmer temperatures (which helps to explain why bait shops need to keep them refrigerated). It’s not uncommon to find anecic worms in the lower reaches of outdoor composting systems - especially in-ground systems - but these worms are definitely not well suited for life in an active composting system, especially not indoor worm bins.

Endogeic Worms

These are the “in-betweeners”; the worms that live in shallower burrows - typically more horizontal in orientation - higher up in the soil profile. They tend to be small to mid-sized and are usually found in higher densities than anecic worms. Based on their more exposed environment, they also tend to be somewhat more tolerant of warmer temperatures, but they’re still soil worms and usually won’t be well-suited for worm composting.

You can think of them as your typical “garden variety” of earthworms - usually the most common group encountered when digging in your flower and vegetable beds.

Epigeic Worms

These worms live at the very top of the soil profile; in fact, very often above the soil in rich deposits of organic matter such as manure heaps or compost piles.

Epigeic worms:

Are often found in very high densities.
Feed actively on richer waste materials.
Tend to breed much more rapidly than other earthworms.
Are more tolerant of warmer temperatures and other climate extremes.
Don’t require any form of soil in their habitat.

In short, they are very well-suited for life in composting systems!

NOTE: It’s important to mention that there is some gray area with these ecological groupings. For example, there are certain varieties of earthworm that are somewhere in between endogeic and epigeic. They live in the upper layers of soil, but they are drawn to deposits of (usually carbon-rich) organic matter, such as dead leaves. These can be some of the more invasive worms - e.g. Lumbricus rubellus, Amynthas sp (“Asian Jumping Worms”) - known for their ability to consume large quantities of leaf litter and other organic matter, potentially having a negative impact on sensitive natural ecosystems. Be sure to check out our article, “Can I Add Red Wigglers to My Garden?” for more information about invasive earthworms.

The Composting Worms - In More Detail

As important as epigeic worms are for the wonderful world of worm composting, there are surprisingly few varieties that are commonly used. Below we outline the main families and species involved.

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Family Lumbricidae

Many of the common genera of soil-dwelling worms in Canada belong to this family (e.g. Lumbricus sp, Allolobophora sp), but it also includes some very important composting worms.

Red (Wiggler) Worms - Tiger Worms - Manure Worms (Eisenia fetida/andrei)

This is the most widely used and versatile of the composting worms, and the variety we always recommend starting with. Red Worms were originally thought to be exclusively Eisenia fetida, but somewhere along the way researchers determined that another closely related species, Eisenia andrei, very often occurs in mixed populations with E. fetida.

As closely related as these two species are, they are unable to interbreed. It’s also important to note that for all the claims being made about ways to distinguish one from the other, there is actually little in the way of convincing evidence (that we are aware of) to accomplish this based on coloration or other physical attributes.

NOTE: Some Red Worms exhibit very distinct banding all along their length (hence the common name “Tiger Worms”). Some people have claimed this is a key distinguishing feature of one variety or the other (they aren’t even consistent about that). The problem, though, is that Red Worms very often change their coloration and striping over time. This seems to relate more to the environment they are living in than on the variety you are working with.

Bottom-line - our recommendation here is to not get too caught up in any of this Eisenia sp ID “drama”. If you find a reliable supplier of “Red Worms” intended for composting, there is a very good chance you’ll end up with the right worms for the job, especially up here in Canada!

European Nightcrawler - “Euro” (Eisenia hortensis)

This is the larger “cousin” of the Red Worm - very often raised and sold as a bait worm. These worms are nearly as versatile as Red Worms in terms of their composting abilities and temperature tolerance, but they can definitely be more temperamental at times. They do not like vibrations, and they’ll often attempt to flee their system if it is getting bumped around too much.

They are also more sensitive to acidic conditions, and not nearly as well suited for upward migration continuous flow (CFT) systems due to their tendency to hang out lower in a habitat than Red Worms.

If you’re curious about the typical size difference between a Euro and a Red Worm, the image below should provide some perspective (Red Worm up top, Euro below).

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Family Eudrilidae

This is a family of tropical earthworms mainly found on the African continent.

African Nightcrawler (Eudrilus eugeniae)

This is the largest of the commonly used composting species, sometimes reaching lengths of more than 10 inches (25 cm). It is known for its voracious appetite and rapid breeding under ideal conditions.

The main limitation of these worms is their intolerance for colder temperatures. Productivity will drop off sharply at temps below 20 C (68 F), and they will typically start to die off once temps fall below 10 C (50 F).

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Family Megascolecidae

This is the earthworm family with the greatest number of species, including some of the largest-bodied varieties in the world (up to 2 metres in length), as well as the invasive “jumper” worms (Amynthas sp) mentioned earlier.

Blue Worms (Perionyx excavatus)

These are talented composters with a bad reputation. Similar to African Nightcrawlers, Blues have voracious appetites and breed very rapidly when conditions are favourable - but they are limited by cooler temperatures, among other… quirks. 😄

In warmer parts of the U.S., Blue Worms have become a common invasive species on worm farms - tending to outcompete Red Worms when both are in the same systems. Some suppliers have even become known for selling “Red Worms” that are primarily batches of Blues.

Apart from their cold intolerance, Blue Worms are also known for roaming - often without any warning.

Fun Fact: This roaming behaviour is very much a part of their nature - not just a response to life in captivity - with some reports of Blues having been found at the top of trees and buildings after storms!

In case you’re wondering, the “good news” is that these worms haven’t been able to thrive in Canada the same way they have south of the border, so you’re far less likely to end up with any in your batches of Red Worms up here.

Still, it doesn’t hurt to be familiar with their key traits:

Very fast, often jerky movement (when conditions are warm).
Thin, streamlined appearance - with a body that tapers at both ends.
Flattened clitellum, very close to the anterior end of the body.
Fairly uniform, dull coloration (no stripes or bright colours), sometimes with a bluish purple sheen.
Show signs of stress when temperatures drop below 15° C (59° F)

Common Names and Other Potential Pitfalls

Some of the ID-related challenges that vermicomposters can face include the widespread use of (often different) common names, improper identification to begin with, or misleading/false claims.

Here are our recommendations:

Buy composting worms from reputable suppliers that provide scientific names.
That being said…don’t get too caught up in the need for 100% “pure” worms (e.g. only Eisenia fetida).
Be wary of anyone that guarantees purity or makes other claims about the superiority of their worms. E.g. there is no such thing as “hybrid earthworms” - different species cannot interbreed!

The good news is that getting the right worms for your worm composting projects is pretty easy these days, so don’t let any of the info shared here discourage or scare you! We simply want to make sure you’re up to speed with most of the ins and outs of earthworm classification and identification, and better prepared to choose the right worms for the job!

Summing Up

There is a wide array of different earthworm species, but surprisingly few that are actually well suited for vermicomposting.
Composting worms are epigeic species that:

1. are tolerant of warmer, crowded conditions,
2. actively feed on rich organic wastes, and
3. breed much more quickly than most of their soil-dwelling counterparts,
4. don’t require any soil in their habitat.

Of the composting species, Red (Wiggler) Worms - Eisenia fetida/andrei - are the most versatile and highly recommended variety.
European Nightcrawlers are great for anyone wanting bigger worms (than Reds), but they tend to be more temperamental and potentially challenging to work with.
African Nightcrawlers and Blue Worms can be superior feeders and breeders - when conditions are favourable - but cold intolerance and restless behaviour (namely in case of Blues) makes them a lot less practical for most people.
Put more stock in scientific names than common names, but don’t get too caught up in trying to track down the perfect, genetically “pure” batch of worms.
Buying worms from a reputable supplier can help to ensure that you hit the ground running with the right worms for your worm composting efforts!

Recommended Products

Hemp Worm Blanket
Red Wigglers
Worm Starter Kit
Worm Rake
pH Buffer Grit
BioChar

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