European Nightcrawler or European Red Worm are common names for the worm which is scientifically called Eisenia hortensis. The euro is a great worm for composting and is quite a bit larger compared to the red wiggler. The size is important primarily to fisherman or exotic pet keepers who need a certain sized worm.
The European red worm is great for composting and is quite a hardy worm in my experience. One of the major differences being that the euro has a tendency to burrow much deeper into the beds and can be found at any depth. If uneaten food becomes buried deep in a bed of only red wiggler they may not consume it and it could become soured, with european red worms in the bed this is not a problem as the feed will get consumed eventually. The downside to this is that the Europeans can be hard to find in the bed and they do not tend to do as well in worm systems that depend upon worms to migrate upwards.
Many people, including experienced worm farmers, have told me that the european red worm reproduces at a much slower rate than the red wiggler. One experienced farmer has told me several times that you will never get more that one worm per egg capsule from the euro. I have found however that these claims are not entirely true. It does take quite some time for the euro to grow to full size and they are fewer worms per egg capsule, but I have seen as many as three worms come out of one egg capsule so I know this to be possible. Also the Euro seem to lay more eggs than the red wiggler, but the Euro is more finicky about the conditions before they will reproduce.
The Euro seems to love a diet high in fiber and low in protein compared to the red wiggler. This is a benefit as high fiber foods are generally easier to find for free or cheap compared to high protein foods. The european worm has quite a thick skin and is able to penetrate much harder ground. This is great is you are having compaction problems in your worm bins or if you would like to add worms to the garden. Even with the Euro worm you must add and incorporate lots of organic matter into the soil before the worm can survive. I think that this worm is a much better choice for use in a garden space over the red wiggler. The thick skin on the Euro also enables it to withstand dry conditions while maintaining a healthy size and appearance. This makes this worm easier to ship as dryer bedding allows for more airflow and less risk of shipping problems.
The Euro’s larger size makes it a better worm for classrooms and other demos. First, it is easier to observe from a distance, making group learning easier. Also any observation on the parts and sections of a worm is easier do to its size. The large egg capsules are easier to spot and then show to groups. Whenever I want show someone a worm egg I always go to the Euros as they are a lot easier to find and show. The Euros appearance seems to invoke less gross responses from the squeamish people, and they are also less slimy and tend to be more active and photo sensitive. This would make them a better choice if showing how worms react to light.
The real big disadvantages to the Euro are its slower reproduction, shorter life span, lack of upwards migration, and sensitivity to environmental conditions. The red wiggler worm will happily keep composting in very high temperatures and even survive compost piles going through minor heat up by moving to the edges. The euro however would likely be killed by these conditions. The euro is in high demand for fishing and this keeps the price much higher than that of the red wiggler. This is likely one of the major keys to its lower usage in compost.
Whichever worm one decides to use or even both worms will result in the best quality compost available. The worm castings from either worm will turn any plant into a thriving growing and greener plant quicker than anything else available. If you are into gardening then you should also be into vermiculture. Worms and their poop do wonders for plants.