My first exposure to Buddhism was watching Seven Years in Tibet in my German childhood. Most memorable were the following two scenes of Buddhist monks in orange robes.
In the one scene, some monks were carefully making a large picture out of coloured sand in a room with large windows. Upon completion (after one year of labour), the monks would simply open the window to let the wind carry the picture away.
In the other scene, monks were very carefully turning soil. Apparently the monks had to be especially careful not to harm any earthworms, because, according to their belief, their mothers would be reincarnated as earthworms.
Needless to say, I found it very arbitrary at best that mothers should be reincarnated as earthworms and was troubled by this first impressions for the next decade or so. Unfortunately, I still haven't been able to solve this mystery.
So my question is, as it has been for many years, is there any connection between mothers and earthworms in Buddhism?