Know Your Friends

Lady Beetles

Ladybug, ladybug, fly away home,
Your house is on fire, your children do roam.
Except little Nan, who sits in a pan,
Weaving gold laces as fast as she can.

Ladybugs or lady beetles have been recognized by many cultures for their predatory behaviors for centuries. Aspects of their biology have been incorporated into folklore and cultures of many Western European countries. The above English nursery rhyme is based upon the ancient practice of burning hop fields following harvest to eliminate aphids. Any larval stages of ladybugs would also face the same fate; only the immobile pupae, attached by their molt skins or "pans" may have developed to the winged adult stage to "fly away home". The family Coccinellidae contains over 4000 species, almost all of these species are predators and feed on many different kinds of soft-bodied insects (e.g. aphids and scales). The common names used for these insect predators include lady beetle, ladybug, or ladybird beetle. Adults of these insect predators are some of the most widely recognized insects in the United States. As early as the late 1800s, lady beetles were being used in biological control programs in the United States. The importation of the predacious vedalia beetle, a scale-feeding lady beetle species, saved the citrus industry in California from the cottony cushion scale. The mealybug destroyer, another lady beetle species, was introduced into California in 1928 and is now commercially available for mealybug suppression. In the Midwest several very common lady beetle species are aphid predators, including the twelvespotted lady beetle, the convergent lady beetle, the sevenspotted lady beetle and the twospotted lady beetle.

The larval stages of these species are not as easily recognized as the adults, but are also predators of pest insects. The size and coloration of the larval stages vary among the species, but generally the larvae are soft bodied and shaped like a miniature alligator. Newly hatched larvae are gray or black and less than 1/8 inch long. Later stage larvae can be gray, black, or blue with bright yellow or orange markings on the body.

Adults of the twelvespotted lady beetle (Coleomegilla maculata) are about 1/4 inch long and have pink to light red colored wing covers with six black spots on each wing. Both adults and larvae feed on aphids, mites, insect eggs, and small larvae of many insect pests including the European corn borer and alfalfa weevil. Plant pollen and fungal spores are also important components of their diet. Females lay clusters of 10 to 20 yellow eggs on plants. This species has two to three generations per year in the Midwest and overwinters as large groups of adults in litter at the base of trees or along buildings.

Adults of the convergent lady beetle (Hippodamia convergens) are also about 1/4 inch long, have orange wing covers, that typically have six small black spots on each wing cover. However, the number of spots can vary, and some adults have no spots on their wing covers. The section of the body behind the head is black with white margins and has two converging white lines the reason for its common name the convergent lady beetle. Adults and larvae feed primarily on aphids. Females lay clusters of 10-20 yellow eggs on plants infested with aphids. The larvae grow and molt through four stages. The life cycle is similar to the twelvespotted lady beetle, but this species probably has one or two generations each year in the Midwest. This species is native to North America.

The sevenspotted lady beetle (Coccinella septempunctata) was introduced into North America from Europe. Adults are large (about 3/8 inch), have red wing covers with seven black spots. Females lay clusters of 15 to 70 yellow eggs on plants that are infested with their aphid prey. Larvae grow and molt through four stages as they feed on aphid prey. The large fourth instar consumes more aphids than the previous three larval stages combined. Adult sevenspotted lady beetles overwinter in small groups in hedges, or in leaf litter on the ground near the base of plants.

The twospotted lady beetle (Adalia bipunctata) is commonly found in trees and bushes, and as one might expect from its common name is red with two black spots. The 1/4 inch long adults overwinter in or around buildings or other protected locations, and emerge in early to mid-spring.

These species of predatory insects are common in most agricultural and garden habitats in the Midwest. Their beneficial predatory behaviors should be recognized and the presence of lady beetles indicates that natural biological control is occurring. Their activity can be encouraged through the reduced use of insecticides or the use of selective insecticides. Also, the planting of a variety of crops or creating habitats for beneficial insects may provide lady beetle species with several types of prey and possible nectar and pollen sources.

-John Obrycki, Iowa State University

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