Worms!

[mike]

They are frequently called Lumbricus rubellus, but probably comprise a mixture of species.
As to the speed at which different species reproduce, that will depend on the conditions, so is going to be different in each case. At higher temperatures (above 20C) Dendrobaenas will often reproduce faster than E.foetida.

 

[jesper]

Not according to Kelly Slocum, actually I have read that hortensis prefer cooler temperatures to foetida. Hortensis are considered a bad compost worm due to its much slower reproduction rate compared to foetida.