Neuroptera

Lore & Background

Neuropterans are soft-bodied insects with large lateral compound eyes and strong mandibles for chewing. Their larvae are specialized predators with elongated mandibles for piercing and sucking, and they lack a connection between the midgut and hindgut, using Malpighian tubules to produce silk for cocoons. Larvae of various families cover themselves in debris as camouflage; antlion larvae bury themselves and ambush prey from pits. Some Ithonidae larvae are root feeders, Sisyridae larvae are aquatic and feed on freshwater sponges, and a few mantispids parasitize spider egg sacs. Adults of many groups are also predatory, though some do not feed or consume only nectar.

Reader's Guide

Neuroptera are significant as predators of pest insects, with many chrysopids, hemerobiids, and coniopterygids eating aphids and other pests, and some have been used for biological control. Their evolutionary history extends from the Permian period, with fossils from Siberia and Australia. The family Kalligrammatidae, known for large patterned wings, lived from the Jurassic to the Aptian period. Following the Cretaceous, neuropteran diversity appears to have declined. Phylogenetic analyses in 2018 and 2023 have clarified relationships within Neuropterida, placing Megaloptera as sister to Neuroptera and Raphidioptera as sister to both. The order's taxonomy has been revised to abandon the paraphyletic suborder Hemerobiiformia and redefine Myrmeleontiformia as a clade. In human culture, Neuroptera have been investigated for biological control, and five species are among insects eaten by humans worldwide.

Did You Know?

• The name Neuroptera comes from Greek words meaning 'nerve' and 'wing'.
• Larvae of the family Sisyridae are aquatic and feed on freshwater sponges.
• Five species of Neuroptera are among 1681 insect species eaten by humans worldwide.

Anatomy and the Architecture of the Wings

Neuropterans are soft-bodied insects whose name derives from Ancient Greek words for "nerve" and "wing," a fitting nod to the dense lattice of veins crisscrossing their four membranous wings. Unlike many other holometabolan groups, these insects lack highly specialised anatomical features; their chewing mouthparts carry strong mandibles without the elaborate adaptations found in other orders. Large lateral compound eyes dominate the head, and ocelli may or may not be present. The wings are typically similar in size and shape, sharing a generalised venation pattern, though some species harbour specialised sense organs within the wing membrane or possess bristles that link the wings together during flight. The larvae present a striking contrast to the adult form: they bear elongated mandibles adapted for piercing and sucking, three pairs of thoracic legs each tipped with two claws, and often adhesive discs on the final two abdominal segments. Notably, the larval gut lacks a connection between midgut and hindgut, and the Malpighian tubules are repurposed to produce silk for cocoon construction, which exits through the anus.

Larval Predation, Camouflage, and the Silk Cocoon

The larval stage of most neuropteran families is a masterclass in predatory specialisation. While adults of many groups remain predatory, some shift to nectar or feed not at all; the larvae, by contrast, are almost universally hunters. Chrysopid, hemerobiid, and coniopterygid larvae target aphids and other small pest insects, making them valuable allies in biological control programmes. Other families push camouflage to extraordinary lengths: antlion larvae bury themselves entirely beneath the soil surface, ambushing prey from self-dug pits, while larvae in various families drape their bodies with debris—living and dead insects alike—to render themselves invisible. A few mantispids have adopted a parasitic strategy, laying eggs in spider egg sacs. The Ithonidae include root-feeding larvae, and the Sisyridae are aquatic, grazing on freshwater sponges. After their predatory phase, the larva spins a cocoon of silk mixed with soil or debris. In Myrmeleontidae and Ascalaphidae, the tenth abdominal segment is modified into a retractable spinneret housed within the ninth segment, dedicated solely to cocoon construction. The pupa eventually cuts free with its mandibles and may even crawl briefly before the final moult to the adult form.

Deep Time: From the Permian to the Mesozoic Peak

Neuropterans are among the oldest winged insects, with their earliest fossils—Permithonidae from the Tunguska basin in Siberia and a comparable fauna from Australia—dating to the late Permian period. Through the Mesozoic era, the group radiated into remarkable diversity, producing several unusually large forms. The extinct family Kalligrammatidae, which persisted from the Jurassic into the Aptian (Lower Cretaceous), earned the evocative nickname "the butterflies of the Jurassic" for their large, elaborately patterned wings. The osmylids, possibly the most ancient extant neuropteran lineage, trace back to the Jurassic or Early Cretaceous, with the fossil Protosmylus preserved in middle Eocene Baltic amber and the genus Burmaleon recovered from Cenomanian Burmese amber, suggesting crown-group radiation in the Early Cretaceous or earlier. Ithonidae span from the Jurassic to the present, with extinct lineages once widespread geographically. Yet following the end of the Cretaceous period, neuropteran diversity appears to have declined, leaving the roughly 6,000 species that compose the order today as a fraction of its Mesozoic peak.

Ecological Roles, Parasitism, and Taxonomic Placement

Within their ecosystems, neuropterans occupy a surprisingly wide range of trophic niches. The larvae of chrysopids, hemerobiids, and coniopterygids are voracious consumers of aphids and other pest insects, and this role has made them practical tools in biological control, available both from commercial distributors and naturally abundant in many habitats. Adults of many groups continue as predators, but others restrict themselves to nectar or do not feed at all. Aquatic sisyrid larvae feed on freshwater sponges, a handful of mantispids parasitise spider egg sacs, and certain Ithonidae larvae are root feeders. Neuropterans are not immune to predation or parasitism themselves: beetles, wasps, and some lake flies are known to parasitise their larvae. In broader taxonomic context, neuropterans are grouped with Megaloptera (alderflies, fishflies, dobsonflies) and Raphidioptera (snakeflies) within the unranked taxon Neuropterida, formerly called Planipennia. A 2023 phylogenomic analysis confirmed the topology of these orders, while a 2018 review by Engel, Winterton, and Breitkreuz restructured internal classification, abandoning the paraphyletic suborder Hemerobiiformia and redefining Myrmeleontiformia as a true clade.