Integumental sensilla and gland openings occur in the integuments of calanoid copepods in what are, essentially, bilaterally symmetrical patterns. Their presence is most easily determined by digestion of the integument in hot alkali to destroy the soft tissues. The sites of the sensilla and gland openings are then seen in the integument, stained with chlorazol black, as spots of light under the light microscope. These pores, or holes, in the integument result from the digestion of the neural innervation of the sensilla or from the digestion of the ducts of the glands which traverse the integument from the epidermis to the outside. The patterns of distribution of these pores are examined in 249 species representing 89 genera ascribed to 28 families of the calanoid copepods. The investigation is confined to the patterns in the five metasomal segments of the species. The metasomal pattern is peculiar to most species and represents a species signature. The pore signature of an individual species consists of several constituent elements. The pores group into several complexes within which individual pores may or may not be developed in that species. The primary elements of these complexes are subscribed to by the signature of the superfamily to which the species belongs. The superfamilial signature with the addition of secondary elements forms the familial signature which is further diversified to form the generic signature. The generic signature is usually further complicated to produce the species signature. In some genera, however, the generic metasomal signature is not complicated to any degree in the constituent species and the distinctive elements of the species pore signature are found more or less restricted to the urosomal segments.
These patterns of pores that can be traced from the species and genus through to the corresponding superfamily form one suite of pores. A second suite of pores is developed within some genera and families that probably represents specialization within these taxa. There is a gradual modification of the pore signatures that corresponds with current concepts of the phylogeny of the Copepoda.