Delicate lacewings and ferocious ant lions don't look like they have much in common but they are both members of the insect order Neuroptera. The lacewing is the adult form and the ant lion is the larval form of this holometabolous insect group. The adults have two pairs of membranous, heavily venated but transparent wings. They have long antennae, chewing mouthparts and large compound eyes. Their bodies are soft with a long abdomen. There are about 5000 described species, so this is not a large order of insects.
Lacewings first appear in the fossil record of the Permian Era, some 250 million years ago and are the oldest and most primitive of the insects that have a complete life cycle (holometabolous: egg to larva to pupa to adult). Most of the life is spent in the larval form and this may last several years.
The most common larvae, known as ant lions, have well developed legs and powerful biting jaws. They make cone-shaped traps in the sand and they sit half buried at the bottom where they wait for their hapless insect victims to fall down. In one family, the larvae are parasitic on spiders and in another, the larvae are aquatic and feed on freshwater sponges.
The adults are much shorter lived, since their main purpose is to disperse and mate. Their flights are short and fluttery and most do not eat. Those that do feed on soft insects like aphids and supplement their diet with pollen. After mating, the females either lay their eggs directly in the soil or attached to stalks that are stuck to wood, leaves or other substrates. After hatching, the predatory larvae eat, grow and moult several times before pupating into the adults.
Neuroptera are found throughout the world but are more common in the tropics. Each area has endemic species so it appears that they do not disperse very effectively. Some are brightly coloured while others are cryptic. They all have a very characteristic way of folding their wings into a steep roof-like position when resting.
Two other groups are now classified with the Neuroptera, although they were once given their own orders. These are the dobson flies and alder flies, suborder Megaloptera, and the snake flies, suborder Raphidoptera. There are some 300 species of alderflies, chiefly found in the temperate regions of the world. They look similar to lacewings but all their larvae are aquatic carnivores. The snake flies have a long 'neck' (prothorax) which gives them a snaky appearance, and a long egg-laying tube in the females. The carnivorous larvae are terrestrial. This is a small group with only about 100 species known.