Lacewings
Also known as Green lacewings, Brown lacewings, Aphid lions, Chrysopidae, Chrysoperla
In short
Lacewings are delicate, net-winged insects whose larvae, nicknamed aphid lions, hunt aphids, mealybugs, thrips, mites and other small soft-bodied pests. The larvae look nothing like the pale green adults and are easy to mistake for a pest. Lacewing eggs stand on fine silk stalks and are a sure sign the predators are nearby.
How it looks
Adult green lacewings are soft-bodied, pale green (some are brown, greyish or reddish), with golden eyes and four clear, finely veined wings held roof-like over the body; they are about 19 mm long. Brown lacewings are roughly half that size and brownish. Eggs are oblong, about 1.5 mm or less, each on the tip of a silk stalk around 1 cm long, usually under leaves; they change from pale green or white to grey before hatching. Larvae are flattened, elongated "tiny alligators" up to about 12 mm, cream to tan with darker markings and large curved jaws; some carry a camouflage pack of debris and old prey skins on their backs.
Signs
Tiny eggs on hair-like stalks on leaves, stems or even pots and walls; active tan larvae moving among aphids or mealybugs; drained, empty aphid skins.
Life cycle
Egg, larva, pupa (in a round silk cocoon) and adult. In warm weather egg to adult takes about 4–6 weeks, and there are several generations a year. A female lays roughly 100–300 eggs in her lifetime.
What favours it
Adults need nectar, pollen and honeydew, so they are commonest where flowering plants grow near pest colonies. Dust, ants and broad-spectrum sprays reduce their numbers.
Prevention
- Leave stalked eggs and debris-carrying larvae alone when cleaning leaves.
- Grow a few flowering plants that offer nectar and pollen near your collection, keep ants off infested plants, and avoid broad-spectrum, persistent insecticides.
- Reduce dust on outdoor plants by occasional overhead rinsing.
Treatment
Start with the first step and move down only if the problem persists.
- No control needed. Where aphids or mealybugs build up on outdoor or greenhouse plants, commercially reared green lacewing eggs or larvae can be released; follow the supplier's instructions.
- If pests must also be sprayed, choose short-residual products such as insecticidal soap or horticultural oil, spot-treat the pest and follow the product label.
Pros and cons
Pros
- Larvae eat a wide range of pests: mites, aphids, small caterpillars, leafhoppers, mealybugs, psyllids, scale insects and thrips.
- Commercially reared and widely used in biological control.
- Adults of many green lacewing species feed only on nectar, pollen and honeydew and do no harm.
Cons
- Larvae are generalists and cannibalistic, and may eat other beneficial insects.
- Larvae occasionally give people a small nip.
- Some adults give off an unpleasant smell when handled.
- Results from releases vary with species and conditions.
Look-alikes
- Ladybird larvae
- Also alligator-shaped, but usually darker (black, grey or bluish) with orange spots and bumpy or bristly backs, and without the long curved jaws.
- Mealybugs
- A debris-covered lacewing larva can look like a clump of fluff, but it walks quickly; mealybugs are slow and waxy white.
- Fungus hyphae or mould threads
- Lacewing egg stalks each end in a single tiny oval egg and are spaced out, not branching threads.
Where you find it
Outdoor ornamentals, vegetables, fruit trees and greenhouse crops carrying aphids, mealybugs, thrips, whiteflies or mites.
Related
Sources
- Green lacewings — UC IPM Natural Enemies Gallery
- Chrysopidae — Wikipedia
- Beneficial Predators — UC IPM Home and Landscape
Written in our own words from these sources. Check a product label before using any treatment.