They are native to Europe, but have been introduced (both intentionally and unintentionally) to every other continent except Antarctica. Tiger worms are also being tested for use in a flushless toilet, currently being trialed in India, Uganda and Myanmar.
E. Fetida also possess a unique natural defense system in their CoreLogic fluid: cells called coelomocytes secrete a protein called Lenin, which is a pore-forming toxin (PUT), which is able to permeability and lose invading cells. It is best at targeting foreign cells whose membranes contain significant amounts of sphingomyelin.
(Lenin is also toxic to organisms lacking sphingomyelin in their cell walls, including B. moratorium, though the pathway is not understood). The only simple way of distinguishing the two species is that E. fetid is sometimes lighter.
Molecular analyses have confirmed their identity as separate species, and breeding experiments have shown that they do produce hybrids. The two worms join criteria, the large, lighter-colored bands which contain the worms reproductive organs, and which are only prominent during the reproduction process.
Both worms then secrete cocoons which contain several eggs each. These cocoons are lemon-shaped and are pale yellow at first, becoming more brownish as the worms inside become mature.
The life expectancy of Eugenia fetid under controlled conditions varies, according to different authors, between one and five years. “Chemical changes during vermicomposting (Eugenia fetid) of sheep manure mixed with cotton industrial wastes”.
^ Orozco, F. H.; Ceará, J.; Trujillo, L. M.; Rig, A. “Vermicomposting of coffee pulp using the earthworm Eugenia fetid : Effects on C and N contents and the availability of nutrients”.
“Vermicomposting of industrially produced wood chips and sewage sludge utilizing Eugenia fetid “. ^ Bruin, Hake; Tengelmann, Julia; Andersen, Christian; Andre, Jörg; Lapse, Matthias (2006-01-01).
“Dissection of the mechanisms of catalytic and antibacterial activity of Lenin, a defense protein of the annelid Eugenia fetid”. ^ Platy, Barbara; Began, Janusz; Pan, Tomasz; Grail, Pawed (2018-09-21).
“Asymmetrical hybridization and gene flow between Eugenia Andrei and E. fetid Lumbricidae earthworms”. ^ Domínguez, Jorge; Orlando, Alberto; Air, Manuel; Monroe, Fernando (2003-01-01).
“Uniparental reproduction of Eugenia fetid and E. Andrei (Oligochaeta: Lumbricidae): evidence of self-insemination: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002”. ^ Neubauer, Edward F.; Hammerstein, Roy; Kaplan, David L. (August 1980).
“Growth of the Earthworm Eugenia Fetid in Relation to Population Density and Food Rationing”. “The life-cycle of the compost worm Eugenia fetid (Oligochaeta)”.
Rather, they thrive in and under leaf litter, manure, decomposing vegetation, and other organic matter. Native to Europe, arena fetid are not classified as invasive species in North America as they are not considered to have a negative environmental impact in the wild.
This species features a vibrant color with yellow banding and is closely related to the more uniformly-pigmented arena Andrei. A study suggests that the two can produce hybrid offspring, a phenomenon which should otherwise be considered impossible between most worm species.
Fun fact: The “fetid” part of the binomial name refers to what some say is a foul-smelling secretion the red wiggler uses to fend off predators. The anatomy of a red wiggler resembles that of other common earthworms; a long-segmented body begins at the pointed head and terminates at a slightly-flatted tail.
A fleshy band called a flagellum features prominently on the body of the red wiggler at roughly 1/3rd of the length of the worm. The digestive tract is simple, starting at the mouth where the worm begins to consume its food before passing it on to the pharynx.
Calciferous glands in the stomach also serve to neutralize acidic foods passing through the worm's digestive tract. The intestine forms the longest part of the worm and is where the majority of digestion takes place via enzymatic processes.
The castings eventually pass through the anus at the end of the worm as capsules coated with a biologically-rich mucus. Red wigglers, like all earthworms, are hermaphroditic, simultaneously possessing both male and female sex organs, both of which are used in the reproduction process.
Two worms of the same species will intertwine around each other's criteria, secreting sperm through their skin, eventually producing a cocoon. If you're curious how quickly red wigglers can reproduce, check out the Urban Worm Calculator.
Red wigglers are a resilient composting worm, tolerant of a wider range of temperature than other species. For instance, its larger cousin, the European Nightcrawler prefers cooler temperatures in the high-60 °F range.
The red wiggler can tolerate both the low and high ends of these ranges, reproducing and processing organic waste well between 55 °F-90 °F. Its cocoons are famously hardy as well, able to withstand prolonged freezing temperatures, staying viable in a suspended state until they are able to hatch in warmer weather.
But red wigglers are nobody's idea of cheap, and the skyrocketing demand for all things garden-related due to the COVID-19 pandemic of 2020 boosted prices of all composting worms. For most commercial worm bins, 1lb is sufficient, but 2 lbs will get you off to a faster start with your waste processing.
You never know what problems or delays you may encounter with your worm bin, so it's helpful to get it set up first to ensure you get off to a good start. This reduces weight, but more importantly, the risk of microbial activity raising the temperatures to deadly levels while the worms are in transit.
Monday's shipments from my Georgia-based preferred supplier often reach California customers on Wednesday. So make sure that your postman is directed to leave your shipment in a shaded, protected environment if you won't be home to receive your worms.
But if you're ordering from PetS mart, PERCO, Walmart, or another large company that is not directly related to the vermicomposting world, be careful! To save on shipping cost, you may want to see if there are any nearby “Mom and Pop” stores through a Google search.
With the appropriate temperature, moisture, pH, and food sources as discussed below, you should achieve higher densities, perhaps 2-3 lbs per square foot or so. This prevents a mucky, muddy vermicompost that will be simply difficult to harvest at best, and a stinky, anaerobic mess at worst.
If needed, ground eggshells and agricultural lime can be used to offset the generally more acidic fruit and vegetable waste. The European Nightcrawler, the larger cousin of the red wiggler, is just as voracious and also makes for a good bait worm.
The African Nightcrawler is a very large composting worm and makes a beautiful, granular cast. The Indian Blue is voracious, but also prefers a warmer climate, and it also exhibits a tendency to escape the bin.
I like to call it the Ford Taurus of vermicomposting worms ; you won't brag to your hardcore composting buddies that you own them, but they will serve you well. Composting worms are not considered invasive at this time due to causing no known harm and having natural prey to keep their populations in balance.
Assuming it is able to adapt to the environment, the tendency to populate and consume in excess is what usually results in harm to the ecosystem. A search for red wigglers under their official name, Eugenia fetid, yields no relevant results on invasive.org, a website that catalogs invasive species of plants, insects, and animals that stand to pose harm in North America (source).
This short video from National Geographic outlines the impact of various types of invasive species and how they harm the environment of non- native territories. When provided with optimum conditions, they can quickly reach population capacity within a worm bin and begin suffering from limited food resources.
However, compost worms have not demonstrated cold tolerance that scientists believe to be essential to thriving in an invasive manner. A study published in the American Midland Naturalist found evidence that red wiggler eggs did not survive well in winter conditions, limiting the likelihood of the species becoming invasive (source).
I have read studies where it was suspected that their tendency to populate and consume in excess could result in limited resources for other species. Invasive issues aside, composting worms provide an excellent method of dealing with discarded food scraps.
While we often think of this as a backyard hobby, worm farming can be put to use on a massive scale to offset landfill waste of kitchen scraps. An airport in North Carolina, for example, composts leftover food from travelers using almost 2 million red wiggler worms (source).
Compost worms pose the potential to be invasive due to their tendency to reproduce and consume in excess. Given the abundance of natural prey, however, along with an inability to thrive in colder conditions, it is unlikely that they will pose a threat to an ecosystem where they are transplanted.
Responsible management of red wigglers is recommended to lessen the likelihood of invasive behaviors in local areas. So if you are worried that your compost worm farm is going to wreak havoc on the ecosystem, you can likely take a deep breath and relax.