Hearts of Pheretima are situated in the segments

What are worm castings?

Give scientific reasons: Earthworm is known as farmer's friend.

Chromophil cells present on the pharynx of an Earthworm take part in the secretion of:

In $Pheretima$,there are red-colored round bodies present above the alimentary canal in the $4^{th}$,$5^{th}$,and $6^{th}$ segments. It is believed that they are involved in:

In earthworms,pairs of hearts are located in which segments?