Tiny lacewings are huge helpers
Many beneficial insects are so small that you may not know they are working to keep your garden’s ecosystem in order. The green lacewings (mostly Chrysopa or Chrysoperla spp.) are among these tiny but helpful insects, protecting your garden from pests during not one but two stages of their life cycle.
The green lacewing goes through four stages of development: egg, larva, pupa and adult. Lacewing eggs are very small, oblong in shape, and are laid individually on the end of a small hair-like stalk attached to a plant. They are typically placed on the underside of leaves in clusters but may be found individually.
There are a few theories about why the lacewing eggs are poised above the plant on the stalk. One theory is that the stalk raises the egg above predatory insects that may reside on the leaf surface. Another theory is that this location helps prevent the newly hatched larvae from eating each other. Once the eggs hatch, the benefit to your garden begins.
Green lacewing larvae have healthy appetites, eating any soft-bodied insect they can fit into their jaws, including their siblings. They primarily feed on aphids but also will prey on thrips, spider mites, mealybugs and scale crawlers. Larvae look like tiny tan or brown alligators with spiky hairs and large, pincer-shaped mouthparts. It is with these mouth parts that the lacewing kills their prey.
The lacewing closes its mouth parts onto its prey while injecting a digestive enzyme. This enzyme liquefies the organs of the prey, which the lacewing then sucks out, leaving a carcass behind. What happens next depends on which species of green lacewing is dining in your garden. “Naked” larvae use their intricate markings to camouflage themselves from predators. “Debris-carrier” lacewings take a different approach to camouflage.
These “debris-carrier” lacewings take the carcasses left behind from their meals and attach them to the spiked hairs covering the surface of their bodies. They may also add small bits of plant debris, soil particles and thread from spider mites to their disguise. The debris-carriers may become completely covered, earning them the nickname “trash bugs.”
Regardless of the method of camouflage used, the goal is to avoid predators, especially the ants that often guard aphid colonies for the honeydew the aphids secrete. The camouflage of the lacewing aids it in being able to prey on the aphids undetected.
After feeding for about two to three weeks, the lacewing larvae pupate inside a cocoon. Their cocoons are spherical, made of silk, and found on plant stems, leaves, and under loose bark. They emerge as adult green lacewings between ½- to ¾-inch long after one to two weeks, depending on temperature.
The adults have bright green, long, slim bodies and translucent wings with visible, light green venation. Adult lacewings feed on nectar and pollen from flowers in addition to the honeydew secretions from aphids. The consumption of honeydew benefits your garden by decreasing the chance of sooty mold developing on your plants from the honeydew.
A surprising fact about adult lacewings is that they have well-developed hearing. Lacewings can detect sound waves, allowing them to hear predators, including bats, from afar. When the lacewing hears that a predator is approaching, it will drop to the ground to avoid being eaten.
Adult lacewings attract a mate of the same species by using their bodies to produce vibrations. After mating, the female lays eggs in an area with an aphid population, and the life cycle begins again. A female lacewing can have several generations per season, laying 100 to 300 eggs in her lifetime.
You can attract green lacewings by growing various flowering plants in your garden throughout the seasons. Plant flowers that are nectar-rich, such as purple coneflower (Echinacea purpurea), New England aster (Symphyotrichum novae-angliae) and butterfly weed (Asclepias tuberosa). Limit pesticide use, as pesticides kill beneficial insects as well as pests.
While it may seem counterintuitive, allow some aphids to be on your plants, as their presence will make the ideal place for adult lacewings to lay their eggs. Lacewings overwinter as adults in leaves and yard debris. Help maintain their overwintering habitat by leaving some fallen leaves and plant debris in your yard during the fall and winter.
Penn State Extension has additional information about green lacewings and other beneficial insects at extension.psu.edu/programs/master-gardener/counties/york/native-plants/fact-sheets/beneficial-insects-in-the-garden.
If you have questions about the green lacewing or other beneficial insects, call the Penn State Extension Master Gardeners of Butler County at their Garden Hotline at 724-287-4761, ext. 7, or email the Master Gardeners at butlermg@psu.edu.
Amy Cirelli is a Penn State Extension Butler County Master Gardener.
