Lacewings are extremely useful predators in the garden or orchard. They are recognised by their delicate lace-like or gauzy wings and may be seen in large numbers, especially at night and on warm evenings. Like many night fliers, they are attracted to lights, so a lantern placed in front of a white sheet at night is a good way to observe the variety of flying insects in a particular area and to check on lacewing activity on the property. Use this technique at various times of the year to build a profile of insect activity. If the house is close to the garden or orchard, leaving the porch light on can be an easy way to observe the small critters that collect around the back door. Remember that lacewings and many other useful insects are small and not strong fliers, so they will not be seen on very windy or rainy nights (when they are sheltering under a leaf). Lacewings may also be identified by a fluttering type flight, something like a butterfly. Some varieties go by the name "golden eye" because of their prominent metallic like eye.
In northern Australia there are very attractive, colourful Chrysopid family lacewings but most of the continent has to be content with two common lacewings, brown and green. In the Adelaide hills there are two commonly found varieties, a brown and green, and a less common larger brown one. The greatest diversity of lacewings is definitely in the tropical north - about 400 species are found in Australia.
They are active in a variety of situations, especially where there is good native tree cover and in apple and citrus orchards. They have a fairly generalist appetite, roaming around searching for any suitably sized prey. Lacewings can provide useful control of aphids, scale, cherry slug, thrips, mealy bugs, whitefly and mites. They may also eat butterfly and moth eggs when they can find them. or even cannibalise their own eggs. Lacewing usefulness is partly explained by a voracious appetite and partly be the fact that two stages of growth, adult and larvae, are predacious (in some varieties the adult eats only honeydew - the sweet exudate from aphids, or nectar and pollen). Some people think lacewings look a little like dragonflies. Indeed some adult lacewings are capable of capturing prey on the wing like dragonflies.
The larvae holds its prey in strong pincers and sucks out the body fluids. They may be seen only by looking carefully as they are well camouflaged. I have noticed that they often line up along stems, twigs or leaf stalks, so that the brown larvae are hard to see against the woody parts. Some lacewings will attach the empty shells of their prey to their own bodies to assist with disguise - a gruesome reminder of their effectiveness.
Eggs are laid on the underside of leaves. They are easily recognised as a small white swelling on the end of a slim, delicate stalk. Observe them with a ten times eyepiece to notice their oval shape. You may find just one or a row of these "eggs on a stalk". They are reasonably well hidden under a leaf but make a delicious meal for a variety of other predatory insects should they be discovered.
One group of lacewings, the Myrmeleontoidea, are famous for their larvae. The scientific name may be impossibly long and difficult to pronounce, but the common name is ant lion. The ant lion is squatter than other lacewing larvae which, appear rather long (it is sometimes said they look like an alligator with big jaws). The ant lion buries itself is sandy or soft soil, at the bottom of a small excavated crater. Only the strong jaws are left protruding from the sand, ready to grip and hold any creature which tumbles down the sides of the crater and pull it down under the surface. If you notice a scattering of small craters. one to two centimetres deep. in exposed soil, chances are they are ant lions.
Encourage lacewings by providing nectar and pollen (ie flowering plants). Umbelliferous plants in flower are especially attractive. An artificial food can be made from vegemite or yeast sprays applied to the plants where you want the lacewings to feed.