Ithonidae

Adults distinguished from other neuropteran families by wing venation characters and overall robust build. Larvae immediately recognizable by their unique scarabaeiform body shape—compact, C-shaped, with shovel-like head and massive mandibles—unlike the slender, predatory larvae with long stylets typical of other lacewings. The combination of subterranean habits and grub-like morphology is diagnostic for the family. Fossil genera assigned to informal groups based on wing venation patterns, particularly the specialized MP and CuA veins characteristic of the Principiala group.

Modern genera occupy two distinct habitat types: arid regions and forested areas. Arid-adapted taxa include Ithone, Varnia, and Oliarces. Forest-dwelling genera inhabit microthermal to lower mesothermal climates, with Polystoechotes punctatus ranging across North American forests south to Panama, and P. gazullai and Fontecilla graphicus in Central Chilean forests. Platystoechotes lineatus is restricted to Sierra Nevada mountain forests in California. Larvae are exclusively subterranean, burrowing in soil.

Modern distribution is disjunct and relictual. Western Hemisphere: three species in Nearctic realm, four in Neotropical realm. Eastern Hemisphere: three genera in Australasian realm (Australia), one in Indomalaya. Specific modern ranges include Australia (Ithone, Megalithone, Varnia), western North America (Oliarces, Platystoechotes, Polystoechotes punctatus), Central America (Adamsiana, Narodona), Mexico (Narodona), and Chile (Polystoechotes gazullai, Fontecilla graphicus). Historical range far broader: fossil evidence from Early Jurassic to Late Eocene across China, Kazakhstan, Kyrgyzstan, Tajikistan, Brazil, England, Denmark, western North America (Colorado, Washington, British Columbia), and Baltic amber. Polystoechotes punctatus has undergone significant range contraction, disappearing from eastern North America by the 1950s and now restricted to western North America.

Mass emergences of adults recorded for Oliarces and Ithone, typically associated with seasonal rains. Specific seasonal activity patterns for other genera not documented.

Larvae are predators, equipped with poison glands and dual channels for subduing prey—contradicting earlier hypotheses of phytophagy. Adult diet varies: at least some species are carnivorous, though comprehensive data lacking for most genera.

Development includes five larval instars, unlike the three typical of most lacewings. First instar is grub-like, resembling scarabaeiform beetle larvae. Larval stage is entirely subterranean. Duration of developmental stages and pupation site not documented.

Larvae are obligate burrowers in soil, using their compact shovel-shaped heads and robust legs for excavation. Mass emergences of adults occur in some genera following seasonal rains. Adults of at least some species are nocturnal or crepuscular, as suggested by reduced visual systems in larvae and adult attraction to lights.

Larvae function as subterranean predators, representing a unique ecological guild among neuropterans. Their specialized morphology indicates adaptation to predation on soil-dwelling invertebrates. Adult predatory habits suggest role as generalist predators in forest and arid ecosystems, though quantitative ecological impact unknown. The family's primitive phylogenetic position and relict distribution make it significant for understanding neuropteran evolution and historical biogeography.

Limited direct interaction with humans. Occasionally encountered by entomologists and naturalists during mass emergence events. Some species have experienced range contraction (notably Polystoechotes punctatus in eastern North America), potentially indicating sensitivity to habitat disturbance or climate change, though causal factors not established. Fossil taxa are important for understanding Mesozoic-Cenozoic insect faunas and phylogenetic relationships within Neuroptera.

• Ascalaphidae (owlflies)Adult owlflies share large size and broad wings with ithonids, but have distinctly clubbed antennae and large divided eyes—features absent in Ithonidae. Larval owlflies are terrestrial predators with elongate bodies and prominent jaws, not subterranean scarabaeiform grubs.
• Myrmeleontidae (antlions)Adult antlions resemble ithonids in general neuropteran wing plan, but have shorter, clubbed antennae and different wing venation. Antlion larvae are pit-building predators in sandy soils with elongate bodies and forward-projecting jaws, contrasting sharply with the burrowing grub-like ithonid larvae.
• Sisyridae (spongillaflies)Larval Sisyridae are unusual among lacewings in being aquatic, feeding on freshwater sponges—completely different habitat and morphology from subterranean ithonid larvae. Adults are much smaller and more delicate than ithonids.
• Former Rapismatidae and PolystoechotidaeThese families have been synonymized with Ithonidae based on phylogenetic analyses; they are no longer considered distinct taxa but rather nested clades within an expanded Ithonidae sensu lato.

Larvae were historically described as carnivorous by Tillyard (1922) based on morphology, then reinterpreted as phytophagous by Faulkner (1990)—the only plant-feeding lacewings known. Recent morphological study (2020) has confirmed predatory habits, with poison glands and dual channels indicating active predation, correcting the phytophagy hypothesis.

• Neuroptera
• primitive lineage
• subterranean larvae
• scarabaeiform
• disjunct distribution
• relict fauna
• fossil record
• predatory larvae
• mass emergence
• soil-dwelling

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Polystoechotes punctata (Fabricius, 1793) (Neuroptera: Ithonidae) in North America: A Changing Distribution Over Time
• A new genus and first Cenozoic fossil record of moth lacewings (Neuroptera: Ithonidae) from the Early Eocene of North America
• Diversity and fossil record of larvae of three groups of lacewings with unusual ecology and functional morphology: Ithonidae, Coniopterygidae and Sisyridae
• Observations on the Biology ofPolystoechotes punctatus(Fabricius) (Neuroptera: Ithonidae): Adult Trophic Status, Description of the Male Reproductive System, and Associations with Mites
• A new moth lacewing genus (Insecta: Neuroptera: Ithonidae) with proliferated and specialized wing venation from the mid-Cretaceous of northern Myanmar
• Unearthing underground predators: The head morphology of larvae of the moth lacewing genus Ithone Newman (Neuroptera: Ithonidae) and its functional and phylogenetic implications
• A New Interesting Moth Lacewing (Neuroptera: Ithonidae) from the Mid-Cretaceous Kachin Amber.
• New Mitochondrial Genomes of Ithonidae (Neuroptera) and Higher Phylogenetic Implications.