Earthworms are nocturnal animals. They lie in the burrows during the day and come out at night for food. Earthworm leaves the burrow only during the rainy season when their burrows are flooded with water.
Fig: External Apertures of Earthworm
(i) Dorsal pores: These are minute openings situated in the mid-dorsal line in the intersegmental grooves commencing from the 10th segment. The coelom communicates to the exterior through these pores and keeps the body surface moist and free from harmful microorganisms.
(ii) Spermathecal openings: Three pairs of openings are situated ventrolaterally in the intersegmental grooves between segments six and seven, seven and eight and eight and nine. These opening can be easily seen in mature worms.
(iii) Openings of oviduct: These are a pair of apertures lying close together on the ventral surface of the 14th segment.
(iv) Openings of Spermiduct: A pair of apertures are situated on the lower side of the 18th segment.
(v) Nephridiopores: Numerous minute openings scattered on the body wall from 14th segment onwards.