Ladybugs

How it works

Females lay clusters of 5–30 yellow-to-orange, oval eggs near aphid, scale or mealybug colonies. The larvae are long-legged, spiny and shaped like tiny alligators. They are black with orange, white or red markings and are harmless to people. A larva feeds for 2–3 weeks, then pupates for 1–2 weeks. Adults move on once prey gets scarce, while the larvae stay and keep searching. Some species have several generations a year, and the adults of some spend the winter clustered under leaf litter or debris. Lady beetles also eat pollen and nectar, and the pink spotted lady beetle gets up to half its diet from pollen.

The convergent lady beetle, Hippodamia convergens, is the species sold. Much of California's population overwinters in large aggregations in the Sierra Nevada and Coast Range foothills. The beetles sold are collected from these overwintering sites, not reared. Most fly away within one or two days of release. In a UC IPM example, one large, heavily infested rose bush needed two releases of about 1,500 beetles each, a week apart. Wild-collected beetles can also carry a microsporidian disease. In lab tests it cut egg production and lifespan, and it passed to three other lady beetle species, including the native two-spotted lady beetle. If you do buy them, UC IPM advises keeping them refrigerated, misting them with water, and releasing them at dusk at the base of infested plants.

The multicoloured Asian lady beetle, Harmonia axyridis, is about ¼–⅓ inch long and tan to red. It has anywhere from no spots to 19, and a black M- or W-shaped mark on the whitish area behind the head. The USDA released it against orchard and pecan pests from the 1960s to the 1990s, and the first US field populations were found in Louisiana in 1988. Outdoors it is a useful aphid predator. From September to November it flies to sunny walls with contrasting trim to find shelter for the winter, and ends up indoors. Inside it stains surfaces, smells, can trigger allergies and occasionally gives a pinprick bite. It does not breed indoors: the beetles seen in spring are the ones that got in the autumn before. Vacuum them up (a stocking in the hose lets you release them), and seal gaps of ⅛ inch or more in late spring or summer.

What it is confused with

Not every orange beetle with spots is a friend, and the stage that eats the most aphids looks nothing like a ladybug.

1. Also goodLady beetle larva — Long, spiny and alligator-shaped, black with orange or white spots. It is often squashed as a pest, but it is the stage that stays with the aphids.
2. Also goodAsian lady beetle — Often larger and more variable than native species, with a black M or W on the white area behind the head. A good aphid predator outdoors, and the one that invades houses in autumn.
3. PestMexican bean beetle — A plant-eating lady beetle: orange, with eight black spots on each wing cover, feeding on bean leaves. Its larvae are yellow and covered in forked spines. See Mexican bean beetle.
4. PestSquash beetle — The other plant-eating lady beetle, with seven spots, on squash, pumpkin and cantaloupe. Its larvae are also yellow and spiny, unlike the dark larvae of the predators.