Updates on the taxonomy of Ilyobius nubilus (Navs, 1933) (Megaloptera: Sialidae: Sialinae) and Ilyobius brasiliensis (Navs, 1936) from southeastern Brazil.

Species of the Neotropical genus Ilyobius Enderlein, 1910 (Megaloptera: Sialidae) are rare and poorly known because adults are infrequently collected in the field and the larvae have restricted habitat in the stream, facts that make obtaining specimens difficult to access for study. Herein we redescribe the female, describe the male and the larva of Ilyobius nubilus (Navs, 1933) based on specimens collected on the coast of So Paulo State. Adults were obtained mainly by rearing larvae in laboratory condition until adult emergence. The holotype for Ilyobius brasiliensis (Navs, 1936) was examined, and we contand that it is a valid species. Therefore, we do not corroborate its synonymy with I. nubilus. Ilyobius nubilus is a member of the I. chilensis group, and the male genitalia structure, described in this work, also supports its inclusion in this species group.

A new species of Ilyobius Enderlein, 1910 (Megaloptera: Sialidae) from a threatened region in the Mantiqueira Mountain range (Brazil).

A new species of Ilyobius Enderlein, 1910 (Megaloptera: Sialidae) from the Brazilian Atlantic Forest is described based on male, female, and larva. Ilyobius erebus sp. nov. is the 11th species in this genus, and the fourth reported in Brazil. In addition, male and female genitalia of I. hauseri (Contreras-Ramos, Fiorentin Urakami, 2005) are redescribed based on the holotype and newly collected specimens at the type locality. Based on the current classification system, I. erebus sp. nov. is placed in the I. chilensis group, which was supported by male and female genital structures. The type locality of the new species is threatened by human impacts, and conservation of its habitat is needed.