Revision of the Nearctic Species of Hygrotus Groups IV, V, and VI (Coleoptera: Dytiscidae)

The keys, synonymy, diagnosis, description, and distribution are presented for species-groups, IV, V, and VI of the Hygrotus (Coleoptera: Dytiscidae) in the nearctic region. See R. D. Anderson (Ann. Entomol. Soc. Am. 64: 503–512; 69: 557–584) for discussion and keys of remaining species-groups within the genus. Figures of the external male genitalia, curiously modified legs of males, and distribution maps are included. This paper and the two published previously constitute a revision of the genus Hygrotus, covering 42 species recognized from the nearctic region. Identification of female specimens of some species still remains difficult and is often subjective.