Green lacewing guide: lifecycle, diet, size - and why green lacewings are a gardener's friend

It’s easy to overlook this denizen of the dark, despite its diaphanous green wings. Only occasionally will this insect come to the light, sitting on a windowpane, before a hint of something unexpected sends them flittering off into the night or simply dropping to the ground and out of sight. Meet the green lacewing.

What is a green lacewing?

The green lacewing (Chrysoperla carnea) is common and widespread insect in the UK, and a welcome inhabitant of gardens and allotments. As larvae, they are the gardener’s friend, on the strength of their monstrous appetite for aphids and other sap-sucking, leaf-shrivelling and bud-blighting pests.

How big are green lacewing?

Green lacewing are about 1-1.5cm long

What do green lacewing look like?

It's not hard to see how this insect got its name. The green lacewing's body is lime green, while their green wings are translucent and intricately veined, which give the impression of lace.

Green lacewing eggs

Look out for the ant-proof eggs of lacewings. They are laid near aphid colonies, but to avoid the attentions of the ants that attend them, they are positioned teetering on the tip of a long, extruded thread. Each lacewing will lay several hundred and larvae emerge from the eggs after three to six days.

Green lacewing larvae

At first glance, the larvae fall somewhere between caterpillar and slug – soft-bodied, lumpy looking grubs – but up close, the camouflaged body is topped with a mean-looking head, sporting a pair of huge, scimitar-shaped jaws. As it grows, it uses these to end the hopes of more than 600 aphids – grabbing them, injecting them with digestive juices and sucking them dry in a ruthless summer campaign.

What do green lacwing eat?

After emerging from its silken cocooned pupa, the more refined and delicate-looking adult lacewing imbibes pollen and sweet liquids, such as nectar and honeydew. Then it will seek out a mate – and this is where it gets fascinating.

How do green lacewings mate?

Lacewings have ears, or rather, two kinds of sound-receptive organs. The first is found in the wings, but they also have them in their legs. Nothing unusual so far, as crickets, grasshoppers, cicadas and many more insects have similar devices. The difference is that lacewings are famously noisy creatures. They ‘sing’ to each other, and sound plays a significant part in their lives. It’s part of a secretly sonic world, out of human listening range, where body parts become instruments, and insects, such as our lacewing, use the resonance of plant fibres to broadcast their music. The sound made by a lacewing goes by the lovely name of tremulation.

When a lacewing tremulates, its abdomen jerks rapidly up and down and parts of its body rub against each other. The insect orchestrates these vibrations into pulses of low-frequency sound that can travel effectively through the air or a dense tangle of undergrowth, announcing their presence to other lacewings.

Males initiate tremulation, and if a receptive female hears this, she will respond with a similar pulse of sound. Eventually, they will start a duet, with the female filling the gaps between the male’s pulses. This is a vital part of the courtship; mating doesn’t happen without it.

Scientists studying these tremulations have noticed that green lacewing have different ‘songs’ in different parts of their range. One in particular, found in the lowlands and the south, has been described as ‘motorboat’, with ‘slow motorboat’ found in the uplands and the north. It is thought that the owners of each ‘sexual signature tune’ belong to different species, with their songs acting as an isolating mechanism.

We are only beginning to understand what this means for the actual number of species in the UK and the places they can be found. To date about 20 species of lacewing have been identified by song alone. However, unless you have the equipment to hear them singing, they can only really be referred to as a member of the green lacewing complex.