Q.worms
I live in Australia and found on my tomato plant at dusk last night a black worm. It was very thick, about a string width and around 2 inches in length. When picked up, it was very strange in how it felt to the touch. I put in on some wood to kill it and it stretched itself into two pieces, like it had a head on either end, and tried to go into different directions – very strange. There was a witness to this because it was hard to believe what was happening. I have looked on internet and cannot even find anything about a black worm. Thanks in advance.

Certified GKH Gardening Expert
There is a worm that would fit that description. The problem is, I am not certain that it lives in Australia. It is called a blackworm (go figure). It likes marshy areas and procreates by splitting its body. Here is more information: https://en.wikipedia.org/wiki/Lumbriculus_variegatus