IPM components

Lacewings - Chrysopidae

Lacewings are insects belonging to the family Chrysopidae (order: Neuroptera). Their larvae, and in some species also the adults, are predators of other insects.

Primary prey: aphids, spider mites (especially red mites), thrips, whitefly, insects eggs, small caterpillars and larvae of beetles.

Description and life cycle

Most adult lacewings are pale green in color. They are about 12-20 mm long, have long thin antennae, and bright, golden eyes. Their wings are large and transparent with a network of veins and pale green color. Adults fly actively, especially in the evening and at night. The adults feed on nectar, pollen and honeydew. The larvae are active predators of small insects, insect eggs, and mites.

Lacewings have very characteristic eggs of oval shape, which are laid at the end of long silken stalks. Initially the eggs are pale green but after a few days the color turns gray. The eggs are small (< 1mm) and are sometimes laid in clusters. Each female can lay several hundreds of eggs. Larvae are gray or brownish in color. They have well-developed legs and are very active. The mouthparts have a pair of large pincers which are use to suck the body contents from their prey. The three larval stages develop in about 2 to 3 weeks. First instar larvae are about 1 mm long.  Third instar larvae are 6 to 8 mm. The larvae construct a silken cocoon in which to pupate, usually in a hidden place on plants. The pupal stage lasts 10 to 14 days.

The duration of the various stages is influenced by temperature. At higher temperatures the development goes quicker. Lacewings can have several generations per year.

Effectiveness

Lacewing larvae are generalist predators. They feed on many different insects, but have a preference for aphids. They have an enormous appetite and each larva can eat between 100 and 600 aphids. Of these, most will be eaten by the third instar larvae.

In crops with hairy or sticky leaves, the larvae may have difficulties in finding prey insects.

Lacewings (Chrysopa sp.) can be mass-reared for use against a variety of pests. In Thailand, the Department of Agricultural Extension (DOAE) has developed rearing facilities and lacewings are made available to farmers for field release. In the USA and several European countries, lacewings are commercially available to farmers.

Being generalists, lacewing larvae will also feed on other beneficial insects.

An adult lacewing.

Conservation

Young larvae are susceptible to drought and may need a source of moisture.

Adult lacewings need nectar or honeydew as food before egg laying and they also feed on pollen. This can be provided to them by planting flowering plants in or around the field. In fruit orchards, small pockets of weeds can be kept for the same reason.

Tolerate low levels of aphids in the crop, as this will help to attract and conserve lacewings. 

The green lacewing appears to have some natural tolerance to several insecticides although there may be considerable variation. Populations tolerant of pyrethroids, organophosphates, and carbaryl have been selected in the laboratory. Still, when lacewings and other natural enemies occur in the field, it is advisable to avoid the use of pesticides.