A few of points on worms, and I must have said this many times over the last 4 years or so on this site. There are 17 species of worms in the UK. Many worms when small all look similar and only an expert in worms (and I doubt there are many even in the worm farming business) can tell the difference. How do I know this? One of my mates is one of a handful of recognised worm "experts" in the UK.
Whilst doing some research regarding worm composting he ordered worm samples from about 10 different suppliers, all but one misidentified the species he asked for.
Given the above statement are we being deliberately deceived? No I don't think so, it's the lack of knowledge by well intentioned business people trying to make a living.
One of the species that inadvertently gets passed off as red worms are small immature bradlings. Also known as tiger worms because of the yellow bands that develop on mature worms. When small (1 -1 1/4 inch) and immature the bands have not developed fully and the yellowing in its bands and therefore it's hardly recognisable, unless you use a magnifying glass on them. Even then the food stuffs they have been fed on may not have been acidic enough to create the yellow liquid.
Now it's said within angling that fish don't like bradlings because of the yellow liquid they contain. Personally, I've had good fish of most species on bradlings. For me they are a proven fish catcher, out fishing in some circumstance other more used species. They also last a very long-time when submerge in water.
The two reasons (proven fish catcher/lasting a long-time in water) I believe they are good are because of the environmental habitat (niche) they occupy in in the soil profile. Brads are a surface/just under the surface worm. This niche is a very hostile and precarious environ to live in. It floods a lot, living there means that the worms are more than likely going to get washed away into brooks, streams, etc and end up in rivers and stillwaters, ultimately and most likely finishing up as food for some aquatic creature, be that fish or invertebrates. To survive in this environment such worms will have evolved a survival strategy and part of the strategy will be to survive for long periods of time submerged in water.
May be it's time I did some research and talked to a few people about worms and knocked it up into an article.