[2] Robert J. Tillyard first described the larvae of Ithone fusca in 1922, noting the unusual grub-like shape, similar to fruit-chafers and June beetles, as unique among Neuroptera species.

[2] The odd larval shape of Ithionidae larvae has been, and continues to be, a subject of interest among entomologists.

[2] Further study by Faulkner in 1990 has shown the immature Ithonidae to be phytophagous, a condition unique among neuropterans.

[1] The remaining modern species Fontecilla graphicus shares habitat with P. gazullai, also inhabiting forests in Central Chile.

Ithonid specimens have been described from fossils dating between the Early Jurassic and the late Eocene, and from sites that indicate a wider geographic range then seen in the modern taxa.

The next grouping of Mesozoic fossils belong to the Cretaceous genus Principiala, which has species described from Brazil, England and tentatively China.

The results of the analysis showed a clear grouping of the three Australian genera Ithone, Megalithone and Varnia in the family Ithonidae, while all the remaining genera are nested into an expanded Polysteochotidae, given the overall interrelation between the groups, the authors opted to combine the two into an expanded single family Ithonidae.

[2] Ithonidae includes a number of extinct genera described from fossils dating between the Early Jurassic and the Late Eocene.