Ladybirds, also known as lady beetles or ladybugs, are small insects recognized globally for their dome-shaped bodies and bright coloration. These beetles are natural predators used in gardening and agriculture as biological control agents. Their reputation stems from their appetite for soft-bodied pests that commonly damage plants. Understanding the diverse diet of the ladybird, which changes throughout its life stages and depends on food availability, reveals its benefit to a healthy ecosystem.
The Primary Diet: Aphids
The relationship between ladybirds and aphids is central to the beetle’s ecological value in most temperate environments. Aphids, which are small sap-sucking insects, constitute the main food source for many species of ladybirds during their active periods. Both the adult ladybird and its larval stage are specialized predators of these garden pests.
The larval stage is highly effective at controlling aphid colonies due to its rapid development. A single ladybird larva can consume between 350 and 400 aphids during the two weeks it takes to reach the pupal stage. For species like the convergent lady beetle, the larva may consume its own body weight in aphids daily. This intense feeding period ensures the larva receives the necessary protein and nutrients for metamorphosis.
Adult ladybirds maintain this predatory behavior, with some species capable of eating up to 50 aphids per day. Over its entire lifespan, an adult ladybird can devour up to 5,000 aphids. The female strategically lays her eggs directly among an established aphid colony, providing the newly hatched larvae with an immediate food supply. Ladybirds reproduce only where the aphid population density is high enough to support the next generation.
Beyond Aphids: Targeting Other Pests
While aphids are the preferred meal, ladybirds are generalist predators and consume a variety of other soft-bodied garden pests. This secondary diet is important when aphid populations crash or when other pests are more abundant.
The secondary targets include:
- Scale insects, which are often immobile and covered in a waxy shell.
- Spider mites that can rapidly defoliate plants.
- Mealybugs, which resemble small pieces of cotton.
- The immature stages of whiteflies and thrips.
Some ladybird species, such as the Mealybug Destroyer (Cryptolaemus montrouzieri), specialize on scale insects and mealybugs.
Ladybirds also consume the eggs of moths and beetles, providing control over pests before they hatch. This broad diet ensures the ladybird remains present in the garden, even when the aphid population is low. However, high-quality reproduction and rapid larval development are best supported by the rich protein and fat content found in their primary aphid diet.
Survival and Supplemental Foods
Ladybirds rely on non-prey foods to survive when insect prey is scarce, especially during the winter or when pest populations are low. These supplemental items serve specific functions for adult maintenance and reproduction. The most important non-prey foods are pollen, nectar, and honeydew.
Nectar and honeydew are high in simple carbohydrates, providing the energy needed for flight and movement. Honeydew is the sugary liquid waste excreted by aphids and scale insects, which ladybirds consume directly from the leaf surface. This sugar source fuels migration and helps the adult ladybird survive long periods of dormancy or diapause during the winter.
Pollen, collected from flowering plants, provides the adult female with the protein and lipids needed to mature her eggs. A diet consisting only of sugar-rich honeydew or nectar will sustain the adult but will not allow her to lay viable eggs. Female ladybirds require this protein from pollen or insect prey to trigger oogenesis and begin a new generation. A diverse garden with ample flowering plants is essential for sustaining a reproductive ladybird population.