The green lacewing (family Chrysopidae) is a highly valued agent in biological pest control. These beneficial insects are commonly introduced into gardens and agricultural settings to naturally manage damaging soft-bodied pests. The primary target for this predator is the aphid, a sap-sucking insect notorious for forming large colonies on plants. Understanding the lacewing’s predatory efficiency is paramount for anyone considering its use.
Consumption Rates During the Larval Stage
The consumption rate is determined entirely by the larval stage, which is the sole predatory phase. This larva is often called the “aphid lion” due to its aggressive hunting behavior and voracious appetite. A single larva can consume a substantial number of aphids within a seven-day period.
A green lacewing larva generally consumes between 20 and 50 aphids per day, depending on the aphid species and size. Extrapolating this daily feeding rate means a single larva can eliminate between 140 and 350 aphids in seven days. Some reports indicate a single larva can consume up to 400 aphids during its entire two-to-three-week larval development.
The consumption rate increases significantly as the larva develops through its three instars. The third and final larval instar is the most voracious, requiring a large amount of nutrition to prepare for pupation. This final stage exhibits the greatest predatory efficiency, consuming more prey than the first two instars combined. While aphids are a primary food source, the larva is a generalist predator and will also feed on other pests like spider mites, thrips, and whiteflies.
The Lacewing Life Cycle and Predatory Focus
The green lacewing’s life cycle is divided into four stages: egg, larva, pupa, and adult. Only the larval stage focuses on pest reduction. The female adult lays eggs individually on slender stalks, which helps protect them from cannibalistic siblings and small predators.
The larval stage typically lasts for about two to three weeks. During this time, the larva uses its sickle-shaped, hollow mandibles to grasp prey. It injects paralyzing venom and digestive enzymes, then sucks out the body fluids. After completing its feeding phase, the larva spins a silken cocoon, usually in a protected location on the plant or in debris.
The pupal stage lasts approximately one to two weeks, after which the adult lacewing emerges. Unlike the larva, the adult lacewing is generally not a predator of aphids. Adults of most common species feed on non-pest items such as pollen, nectar, and honeydew, which are necessary for energy and successful reproduction. The maximum predatory impact occurs during the brief, intense larval period.
Integrating Lacewings into a Pest Management Strategy
Effectively utilizing green lacewings involves understanding the needs of both the predatory larvae and the reproductive adults. Since larvae are the only stage that actively controls pests, releasing them directly into areas with active infestations provides the quickest means of control. For severe outbreaks, releasing larvae is a practical approach for immediate impact.
To establish a lasting population, encourage adult lacewings to remain and reproduce by providing a suitable habitat. This involves offering necessary food sources for the adults. Planting flowers and herbs that produce nectar and pollen, such as dill, fennel, or yarrow, ensures the adults have the nutrition required to lay hundreds of eggs.
Timing the release of lacewings is a key factor in a management strategy. Releasing them early in the season or shortly after a pest problem is noticed can prevent populations from reaching damaging levels. Additionally, controlling ant populations is often necessary because ants protect aphids in exchange for their sugary honeydew, which interferes with the larvae’s predation efforts.