Key to species of Haplonema

1 Head with four submedian double papillae, two lateral amphids, and six radially arranged ridges; males with 11 pairs caudal papillae and one unpaired median pre-cloacal papilla; vulva protruding beyond body wall................ H. hamulatum

- Head with four submedian single papillae, and two lateral amphids, lacking radially arranged ridges; males with 10 pairs caudal papillae, lacking an unpaired papilla; vulva not protruding beyond body wall........................ H. immutatum