Chrysoperla is a genus of common green lacewings (family Chrysopidae). These delicate, pale green insects are recognized by their large, transparent, finely veined wings and prominent golden eyes. While adult lacewings primarily feed on nectar, pollen, and honeydew, their larvae are highly predatory. This makes them valuable natural enemies of various agricultural pests, leading to their widespread use in biological pest control systems in agricultural fields, gardens, and greenhouses.
Life Stages and Appearance
Chrysoperla undergoes a complete metamorphosis, progressing through four distinct life stages: egg, larva, pupa, and adult. The life cycle can be as short as four weeks in warm conditions, with multiple generations occurring annually.
The female lacewing lays small, oval-shaped eggs, typically pale green or white, often individually or in small clusters on plant foliage. Each egg is characteristically attached to the plant surface by a slender stalk, a feature believed to protect them from predators. Larvae hatch from these eggs within three to six days and are initially around one millimeter long.
These larvae, sometimes called “aphid lions,” are brown or grayish, resembling small alligators with well-developed legs and large, pincer-like mandibles. They grow to about 6-8 millimeters before pupating. The larval stage typically lasts two to three weeks, during which they progress through three instars, each increasing in size and predatory capacity.
When ready, the larva spins a circular, off-white, egg-shaped cocoon, about 3 mm long, usually in a sheltered location on the plant or even on the ground. The pupal stage lasts approximately one week, after which the adult lacewing emerges, ready to reproduce. Adult lacewings are typically 12-20 mm long, with a delicate appearance and long, threadlike antennae.
Natural Predatory Behavior
The predatory behavior of Chrysoperla is exclusively observed in its larval stage. These “aphid lions” are voracious generalist predators, consuming a wide range of soft-bodied insect pests. Their primary prey includes various species of aphids, but they also feed on spider mites, thrips, whiteflies, mealybugs, leafhopper eggs, small caterpillars, and beetle larvae.
When a larva encounters prey, it grasps the victim with its pincer-like mandibles, sometimes lifting the prey off the leaf surface to prevent escape. The larva then injects digestive enzymes into the prey’s body, dissolving its internal organs, and sucks out the liquefied body fluids. A single lacewing larva can consume a significant number of pests, eating between 100 and 600 aphids during its larval development, or over 200 pests or pest eggs in a week.
Utilizing Chrysoperla in Pest Control
Chrysoperla species, particularly Chrysoperla carnea and Chrysoperla rufilabris, are widely utilized in biological pest control programs. They are mass-reared and commercially available, often shipped as eggs, young larvae, or pupae.
For effective control, Chrysoperla can be released at the beginning of a growing season or when pest infestations are low, with recommended introduction rates typically ranging from 10-100 eggs per square meter for preventive measures. In cases of moderate to severe infestations, weekly or bi-weekly releases of eggs or larvae are suggested to ensure a continuous supply of predators. The larvae are applied directly to infested leaves or through specialized application boxes. Chrysoperla carnea is effective across a wide temperature range, including temperatures above 12°C (54°F), with optimal effectiveness between 20-28°C (68-82°F). The use of biological control agents like Chrysoperla reduces reliance on chemical pesticides, thereby mitigating associated environmental and health hazards.