Neuroptera

Neuroptera (from the Ancient Greek neuron, "nerve / sinew," and pteron, "wing," referring to the dense, reticulate network of cross-veins and end-twigging veins across the four membranous wings; also termed Planipennia) is an order of holometabolous (complete-metamorphosis) insects comprising approximately 6,000 extant species across 15 families, including green lacewings (Chrysopidae), brown lacewings (Hemerobiidae), antlions and owlflies (Myrmeleontidae including Ascalaphinae), mantidflies (Mantispidae), spongillaflies (Sisyridae), and thread-winged and spoon-winged lacewings (Nemopteridae). Together with Megaloptera (dobsonflies and alderflies) and Raphidioptera (snakeflies), Neuroptera forms the superorder Neuropterida—the sister clade to Coleoptera (beetles) and Strepsiptera within the holometabolous clade Coleopterida.

While adult neuropterans are typically delicate, weak-flying predators or pollen/nectar feeders with large compound eyes and roof-like wings, every neuropteran larva is a voracious specialized predator defined by three unique anatomical and physiological synapomorphies:

1. Coaxial Suctorial Jaws (Mandible–Maxilla Venom/Suction Forceps): The larval mouthparts lack a true open mouth opening; instead, the elongated, sickle-shaped mandible and maxilla on each side interlock along a tongue-and-groove track to enclose a hollow food and venom canal. The larva impales prey with both jaws, injects paralyzing neurotoxins and histolytic digestive enzymes (produced by both the larva and symbiotic gut bacteria), and sucks the liquefied tissues back up through the hollow jaws.
2. Closed Midgut–Hindgut Junction in Larvae: Throughout its entire larval development, the lumen between the midgut (ventriculus) and the hindgut is anatomically sealed off by a solid cellular plug! Because its liquid diet of hemolymph and digested prey tissues leaves almost zero solid residue, the larva never defecates during larval life, accumulating dark uric-acid/guanine metabolic waste in the blind midgut until it is expelled all at once as a single black pellet (meconium) immediately after adult eclosion.
3. Anal Silk Spinning via Modified Malpighian Tubules: Because the hindgut is freed from fecal excretion during larval life, the larva's Malpighian tubules switch function in the final instar from osmoregulation to silk protein synthesis, secreting liquid silk into the hindgut that is extruded from a telescoping anal spinneret at the tip of the abdomen to weave a spherical pupal cocoon.

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Superorder Neuropterida (Permian divergence, ~280 Ma) ├── Order Raphidioptera (Snakeflies: ~250 spp.; elongated prothorax & long ovipositor) ├── Order Megaloptera (Alderflies, Dobsonflies, & Fishflies: ~380 spp.; aquatic larvae with biting jaws; *Corydalus*) └── Order Neuroptera (Net-Winged Insects: ~6,000 spp.; larval suctorial mandible–maxilla tubes) ├── Suborder Nevrorthiformia — Family Nevrorthidae (Basal aquatic stream larvae; ~20 spp.) ├── Suborder Hemerobiiformia (Lacewings, Mantidflies, & Spongeflies) │ ├── Family Chrysopidae (Green Lacewings: ~1,400 spp.; *Chrysoperla carnea*, *Chrysopa*; stalked eggs, aphid lions) │ ├── Family Hemerobiidae (Brown Lacewings: ~550 spp.; *Hemerobius*, *Micromus*) │ ├── Family Coniopterygidae (Dustywings: ~570 spp.; 2–4 mm wings coated in waxy white *aleurodiform* powder) │ ├── Family Mantispidae (Mantidflies: ~400 spp.; convergent raptorial praying-mantis forelegs; spider egg-sac hypermetamorphosis) │ └── Family Sisyridae (Spongillaflies: ~70 spp.; aquatic larvae pierce freshwater sponges [*Spongilla*] with flexible stylet jaws) │ └── Suborder Myrmeleontiformia (Antlions, Owlflies, & Lacewing Giants; Mesozoic–Cenozoic crown radiation) ├── Family Psychopsidae (Silky Lacewings) & Family Ithonidae (Moth Lacewings) ├── Family Nemopteridae (Spoon-winged & Thread-winged Lacewings: hindwings elongated into ribbon streamers; cave nymphs) ├── Family Nymphidae (Split-footed Lacewings: Australia/New Guinea; basal ancestor of antlions) └── Family Myrmeleontidae (Antlions & Owlflies: >2,100 spp., the largest family in Neuroptera) ├── Subfamily Myrmeleontinae (True Antlions: *Myrmeleon*, *Euroleon*, *Glenurus*; conical sand-pit trap builders) └── Subfamily Ascalaphinae (Owlflies: ~450 spp.; *Libelloides*, *Ululodes*; long clubbed antennae, diurnal dragonfly-like hunters) *`

(Note: During the Jurassic and Early Cretaceous—preserved in Burmese and Spanish amber—extinct myrmeleontiform families such as †Kalligrammatidae evolved giant 15–30 cm butterfly-like wings with eyespots and long tubular siphonate proboscises that fed on Bennettitales/cycad pollination drops 50 million years before true butterflies [Lepidoptera] evolved!)

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Larvae of the subfamily Myrmeleontinae ("doodlebugs") construct one of the animal kingdom's most sophisticated physical traps by exploiting the statistical mechanics of granular media:

1. Spiral Excavation and Differential Grain-Size Sorting: Walking exclusively backward in narrowing concentric spirals while using its flattened head and mandibles like a mechanical shovel to flick sand outward at 45–60°, an antlion larva (Myrmeleon formicarius, Euroleon nostras) excavates a conical pit in dry sand. Crucially, because smaller, lighter sand grains experience higher aerodynamic drag relative to their momentum when flicked into the air (or because larger grains roll back down the slope into the center to be flicked out a second time), the antlion automatically ejects coarse grains onto the outer rim while lining the inner walls of the cone exclusively with fine, low-friction silica grains.
2. Poised at the Critical Angle of Repose (\theta_r ≈ 33°–35°): The finished cone walls sit at the exact critical angle of repose (a self-organized critical state where static shear stress equals maximum Coulomb friction). When a foraging ant (Hymenoptera) steps onto the fine-grained inner slope, its footsteps trigger a localized granular avalanche on which the ant cannot gain traction.
3. Vibrational Localization via Campaniform/Scolopidial Sensilla: Buried at the apex of the cone with only its open sickle jaws protruding, the antlion detects Rayleigh and compressional surface waves generated by the struggling ant's footsteps (amplitude <1 nanometer, propagated through quartz sand grains at 40–60 m/s) via tufts of mechanosensory bristles on its mesothorax and abdomen—computing the prey's azimuth from 0.1-millisecond inter-tuft arrival-time differences and tossing targeted volleys of sand upward to undermine the slope and tumble the ant directly into its jaws.
4. Endosymbiotic Bacterial Neurotoxins (Enterobacter aerogenes): When the antlion bites an ant two to five times its own body mass, the prey is paralyzed within 30 to 60 seconds. Remarkably, a major component of this paralytic venom is groEL—a mutated chaperonin protein secreted by mutualistic bacteria (Enterobacter aerogenes and Bacillus cereus) living inside the antlion's crop and esophageal diverticulum, which possessed 4 residues differing from standard E. coli GroEL that convert the housekeeping folding chaperone into a potent insect-specific neurotoxin!

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Green lacewings (Chrysoperla carnea, Chrysopa oculata) are among the most important beneficial predators in global agricultural biological control, with a single larva ("aphid lion") consuming 200 to 600 aphids (Hemiptera), mealybugs, whiteflies, and spider mites over its two-week larval life:

• Stalked Eggs on Elastomeric Silk Pedicels: Because newly hatched lacewing larvae are cannibalistic (and because foraging ants patrol aphid colonies to kill predators), female green lacewings touch the tip of the abdomen to a leaf, pull upward to draw out a 5- to 15-mm vertical thread of cross-linked β-sheet protein, and cement a single oval egg at the tip of the stiff pedicel—suspending each embryo out of reach of both sibling cannibals and patrolling ants. Furthermore, in Mallada and Ceraeochrysa, the female coats the egg stalk in droplets of defensive squalene and long-chain aldehydes that repel ants.
• Trash-Carrying Camouflage ("Junk Bugs"): Larvae of the genera Chrysopa, Ceraeochrysa, and Leucochrysa bear long, hooked dorsal tubercles on their thorax and abdomen onto which they load the drained exoskeletons of their aphid prey, waxy wool from woolly aphids, and lichen fragments. This portable "debris cloak" provides physical armor and chemical camouflage: when a Chrysopa slossonae larva wears waxy fluff stolen from the woolly alder aphid (Prociphilus tessellatus), aphid-tending carpenter ants (Camponotus) fail to recognize the predator's cuticular hydrocarbons and allow the "wolf in sheep's clothing" to devour the aphid herd unmolested!
• Radial-Vein Tympanal Ears and Bat Evasion: Flying at night, adult green lacewings face intense predation from echolocating bats. Located inside the swollen base of the forewing radial vein is the smallest known insect tympanal ear (~1.5 mm long), innervated by ~25 scolopidial receptors tuned to 15–120 kHz ultrasound. When a hunting bat's echolocation calls transition from low-repetition search phase (~10 pulses/s) to a high-repetition terminal feeding buzz (>100 pulses/s), the lacewing's wing-vein ear triggers an immediate all-or-none reflex fold of all four wings, causing the insect to drop passively in a vertical free-fall out of the bat's flight path in less than 40 milliseconds!

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1. Engel, M. S., Winterton, S. L., & Breitkreuz, L. C. (2018). Phylogeny and evolution of Neuropterida: where have wings of lace taken us? Annual Review of Entomology, 63, 531–551. Google Scholar

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• Insecta
• Coleoptera
• Hemiptera
• Hymenoptera
• Sensory Transduction