The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 4,000 species. Traditionally, the group that was once known as Planipennia, with the Neuroptera at that time also including alderflies, fishflies, dobsonflies and snakeflies, but these are now generally considered to be separate orders (the Megaloptera and Raphidioptera). Sometimes the name Neuropterida is used to refer to these three orders as a group. This is either placed at superorder rank, with the Endopterygota becoming an unranked clade above it, or the Endopterygota are maintained as a superorder, with an unranked Neuropterida being a part of them. Within the endopterygotes, the closest living relatives of the neuropteridan clade are the beetles. The common name lacewings is often used for the most widely known net-winges insects - the green lacewings (Chrysopidae) - but actually most members of the Neuroptera are referred to as some sort of "lacewing".
Neuropterans first appeared during the Permian Period, and continued to diversify through the Mesozoic Era. During this time several unusually large forms evolved, especially in the extinct family Kalligrammatidae, often referred to as "the butterflies of the Jurassic" due to their large, patterned wings.
The larvae of most families are predators. Many chrysopids eat aphids and other pest insects, and have been used for biological control (either from commercial distributors but also abundant and widespread in nature). Larvae in various families cover themselves in debris (sometimes including dead prey insects) as camouflage, taken to an extreme in the ant lions, which bury themselves completely out of sight and ambush prey from "pits" in the soil. Larvae of some Ithonidae are root feeders, and larvae of Sisyridae are aquatic, and feed on freshwater sponges. A few mantispids are parasites of spider egg sacs.
As in other holometabolic orders, there is a pupal stage, generally enclosed in some form of cocoon composed of silk and soil or other debris. Adults of many groups are also predatory, but some do not feed, or consume only nectar.
Apart from a few groups that are quite basal or of uncertain position, the net-winged insects can be divided into two suborders, the Myrmeleontiformia and the Hemerobiiformia. The primitive Nevrorthidae, the most ancient group of living neuropterans, are sometimes considered a third suborder Nevrorthiformia or included in the Hemerobiiformia and more specifically in the Osmyloidea. But actually they are better considered a very basal lineage.
Basal and unresolved forms