They are the external openings of the excretory organs, the nephridia and are located just posterior to inter-segmental grooves on the lateral side and are usually kept close by sphincter muscles. Nephridiopores are very small and generally not easy to recognize. These pores, however, can be seen under high magnification in the case of species having one pair of large nephridia in each segment, in that case may be in a single or two ranks e.g. Perionyx sansibaricus.

Fig: A view of alternate arrangement of nephridiopores in Perionyx sansibaricus