Ithonidae, commonly called moth lacewings and giant lacewings, is a small family of winged insects of the insect order Neuroptera. The family contains a total of ten living genera, and over a dozen extinct genera described from fossils. The modern Ithonids have a notably disjunct distribution, while the extinct genera had a more global range. The family is considered one of the most primitive living neuropteran families. The family has been expanded twice, first to include the genus Rapisma, formerly placed in the monotypic family Rapismatidae, and then in 2010 to include the genera that had been placed into the family Polystoechotidae. Both Rapismatidae and Polystoechotidae have been shown to nest into Ithonidae sensu lato. The larvae of ithonids are grub-like, subterranean and likely phytophagous (plant feeding).
Ithonidae are typically medium to large-sized neuropterans.[1] P. S. Welch conducted research in 1914 on "Polystoechotidae" larvae resulting in the conclusion that the larvae were carnivorous.[2] The larvae live a subterranean life.[3] The first instar stage for modern larvae is grub-like, resembling those of scarabdeiform beetles.[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. Tillyard suggested the larvae to be carnivorous, preying upon Scarabaeidae larvae, attacking with the large mandibles and "sucking them dry".[2] Further study by Faulkner in 1990 has shown the immature Ithonidae to be phytophagous, a condition unique among neuropterans.[2] The adults of at least some ithonids are carnivorous.[4] Mass emergences have been recorded from the genera Oliarces and Ithone, usually associated with seasonal rains.[5]
Modern Ithonidae genera are distributed in both the Western and Eastern Hemispheres, with three species in the Nearctic realm, and four in the Neotropical realm of the Western Hemisphere. Of the genera in the Eastern Hemisphere, three are found in the Australasian realm and one in Indomalaya. The habitats are varied with the genera falling into two general groups, arid taxa and forest taxa.[1] Those genera found in arid regions are Ithone, Varnia, andOliarces.[1] Four of the Neotropical species inhabit areas with forested microthermal to lower mesothermal climates.[1]Polystoechotes has the widest modern range with P. punctatus inhabiting forests across North America south along the mountains to Panama and P. gazullai inhabiting forests in Central Chile. The North American range of P. punctatus has diminished, disappearing from eastern North America by the 1950s,[6] and now appears restricted to Western North America.[1]Platystoechotes lineatus, the sole species in Platystoechotes, is restricted in range to the Sierra Nevada mountains in California, USA.[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.[1] Early genera from the Jurassic have been found in China, Kazakhstan, Kyrgyzstan, and Tajikistan. The next grouping of Mesozoic fossils belong to the Cretaceous genus Principiala, which has species described from Brazil, England and tentatively China. The youngest paleorange for the family includes sites in western North America such as the Florissant formation in Colorado and the Okanagan Highland sites in Washington, USA and British Columbia, Canada.[1] Species of the genus Palaeopsychops have been found in the Eocene Fur Formation of Denmark. The genus Elektrithone, described in 2014, extended the family's fossil range to include Baltic amber.[7]