Lacewings are delicate, gauzy-winged insects belonging to the order Neuroptera. The most familiar species in the UK are the green lacewings (family Chrysopidae), particularly Chrysoperla carnea, and the brown lacewings (family Hemerobiidae). With their translucent, intricately veined wings and bright green or brown bodies, they are among the most elegant garden insects. More importantly, they are among the most beneficial.
Identification
| Feature | Green Lacewing (Chrysopidae) | Brown Lacewing (Hemerobiidae) |
|---|---|---|
| Body colour | Bright green (may turn brownish in autumn) | Brown or greyish-brown |
| Wing span | 25–40 mm | 10–20 mm |
| Eyes | Golden or coppery, conspicuous | Dark, less prominent |
| Antennae | Long, thread-like | Shorter, beaded |
| Behaviour at rest | Wings held tent-like over body | Wings held tent-like over body |
| Active period | Dusk and night; attracted to lights | Day and night |
Life Cycle
Lacewings undergo complete metamorphosis with four stages: egg, larva, pupa, and adult. The eggs of green lacewings are distinctive — each egg is laid on the tip of a slender, hair-like silk stalk attached to a leaf. This elevated position protects the egg from predation by ants and from being eaten by its own siblings.
The Larval Stage: The “Aphid Lion”
It is the larval stage that makes lacewings so valuable. Lacewing larvae are small (up to about 8 mm), flattened, alligator-shaped creatures with prominent, curved, hollow mandibles. They are voracious predators of soft-bodied insects, particularly aphids, and have earned the nickname “aphid lions”.
What Lacewing Larvae Eat
- Aphids — the primary prey; a single larva can consume 200–600 aphids during its development
- Whiteflies — both nymphs and adults
- Mealybugs — soft-bodied scale insects
- Spider mites — particularly red spider mites
- Thrips — small plant-feeding insects
- Small caterpillars and moth eggs
- Other lacewing larvae — they are cannibalistic when prey is scarce
The larva feeds by piercing its prey with its hollow, sickle-shaped mandibles and sucking out the body fluids. It is a remarkably efficient predator. Some species of lacewing larvae camouflage themselves by piling the empty skins of consumed aphids onto their backs, creating a disguise that may also deter predators.
Did you know? A single green lacewing larva can devour up to 600 aphids during its two-to-three-week larval stage. This makes them more effective aphid predators, per individual, than ladybird larvae.
Are Lacewings Beneficial?
Absolutely. Lacewings are considered one of the most important groups of beneficial insects in both garden and agricultural settings. Their value comes from several factors:
- Voracious appetite: Lacewing larvae consume enormous numbers of pest insects, providing significant biological control of aphids, whiteflies, and mites.
- Wide prey range: Unlike some biocontrol agents that target only one pest, lacewing larvae are generalist predators that attack multiple pest species.
- Commercial availability: Green lacewing eggs and larvae are commercially reared and sold for release in greenhouses and gardens as a biological pest control method.
- Compatibility with organic gardening: Using lacewings reduces or eliminates the need for chemical insecticides.
- Adult pollination: Adult green lacewings feed on nectar, honeydew, and pollen, providing supplementary pollination services.
How to Attract Lacewings to Your Garden
Encouraging lacewing populations is straightforward and highly rewarding for gardeners:
Tips for Attracting Lacewings
- Plant nectar-rich flowers: Dill, fennel, yarrow, tansy, and cosmos provide food for adults
- Avoid broad-spectrum pesticides: These kill lacewings along with pest species
- Provide overwintering shelter: Lacewing hotels (bundles of corrugated cardboard in a waterproof container) give adults somewhere to hibernate
- Tolerate some aphids: A small aphid population is necessary to sustain lacewing larvae
- Leave areas of long grass and leaf litter: These provide shelter and hunting grounds
Key Takeaway
Lacewings are among the most beneficial insects a gardener can encourage. Their larvae — the “aphid lions” — are voracious predators of aphids, whiteflies, and mites, making them invaluable for organic pest control. Attracting lacewings is as simple as planting nectar-rich flowers, avoiding pesticides, and providing overwintering habitat.