The body of the lacewing is slender and elongated, and its colour is green to yellow-green. Lacewings look a little like mosquitoes, but the wings are much larger, rounder and show their fine veins clearly. In rest, the wings are folded away on its back like a canopy, while in flight they glisten with a pearly sheen. It is certainly not a quick or agile flyer and it can easily be snatched out of the air. All four of its wings have the same shape and can move independently of each other. Lacewings are vulnerable; the wings are easily damaged, whereupon it will no longer be able to fly to the plants it feeds on.
Lacewings come in many species and sizes, the other well-known one being the Brown lacewing (Micromus variegatus), which is less common. The Green lacewing is found all over the world, with the exception of Australia and Antarctica.
It is handy that this lacewing eats enormous quantities of aphids, especially when they are larvae. The imago (adult) mainly feeds on the secretions of aphids (honeydew) and pollen. Females also eat the odd aphid, especially when they are pregnant with eggs. Aphids are the exclusive food of the larvae, which are veritable eating machines and look a little like the larvae of ladybirds.
The aphids are not actually eaten but sucked dry, as are red spider mites and whitefly, two other plant pests. In greenhouse horticulture especially, lacewings are used en masse to clean up aphid infestations. A single larva can gobble up to 50 aphids a day.
The eggs are laid in between aphid colonies, and are on long stalks. These stalks are designed to keep the eggs clear of ants, which enjoy the honeydew secreted by the aphids, which they protect. The larva is broad and caterpillar-like and has a brown, irregular colour, three pairs of little legs and long, pincer-like mandibles (jaws).
Some species of lacewing larvae camouflage themselves with bits of plant or dead aphid in order to hide from ants. When after some time the larvae pupates a web is spun amongst the vegetation. There are two generations a year, and in the winter the imago hibernates, often in houses. During this resting period the lacewing turns brown, but in the spring it turns green again.