The alderfly genus Ilyobius Enderlein, 1910 is one of the rare groups of Sialidae and mainly distributed in the Neotropical region. Here we describe a new species, I. curvata sp. n., from Panama and Colombia. Furthermore, we provide re-description on two described species of Ilyobius, i.e., I. flavicollis (Enderlein, 1910) and I. nubila (Navás, 1933). A key to the species of Ilyobius is given. The geographical distribution pattern of extant Ilyobius species is also summarized.