Eisenia fetida (older spelling: foetida), known under various common names such as redworm, brandling worm, panfish worm, trout worm, tiger worm, red wiggler worm, etc., is a species of earthworm adapted to decaying organic material. These worms thrive in rotting vegetation, compost, and manure. They are epigean, rarely found in soil. In this trait, they resemble Lumbricus rubellus.
They have groups of bristles (called setae) on each segment that move in and out to grip nearby surfaces as the worms stretch and contract their muscles to push themselves forward or backward.
E. fetida worms are used for vermicomposting of both domestic and industrial organic waste. 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 trialled in India, Uganda and Myanmar.
E. fetida also possess a unique natural defense system in their coelomic fluid: cells called coelomocytes secrete a protein called lysenin, which is a pore-forming toxin (PFT), which is able to permeabilize and lyse invading cells. It is best at targeting foreign cells whose membranes contain significant amounts of sphingomyelin. (Lysenin is also toxic to organisms lacking sphingomyelin in their cell walls, including B. megaterium, though the pathway is not understood). 
E. fetida is closely related to E. andrei, also referred to as E. f. andrei. The only simple way of distinguishing the two species is that E. fetida is sometimes lighter in colour. Molecular analyses have confirmed their identity as separate species, and breeding experiments have shown that they do produce hybrids. 
As with other earthworm species, E. fetida is hermaphroditic, and uniparental reproduction is possible, even if usually the reproduction is between copulating individuals. The two worms join clitella, the large, lighter-colored bands which contain the worms' reproductive organs, and which are only prominent during the reproduction process. The two worms exchange sperm. 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. These cocoons are clearly visible to the naked eye.
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- "Friday Fellow: Tiger Worm" at Earthling Nature.