During the Middle Ages ladybugs would rid grapevines of aphids. In appreciation, these beetles were dedicated to “Our Lady”, hence the name. In Britain and parts of the United States ladybug beetles are called lady bird beetles. Lady Bird Johnson, President Johnson’s wife, got her nickname when a nanny said, “She is as pretty as a lady bird!” and the name stuck. (Lady Bird’s given name was Claudia.)
Ladybug beetles go through a complete metamorphosis during their life cycle. In late spring or early summer the ladybug lays 5 – 30 spindle shaped eggs at a time in clusters attached to twigs or leaves. A female can lay 300 to 500 eggs in a season. The larvae, which resemble miniature black alligators with orange spots, feed on aphids and molt 4 times in about a month before attaching to a twig or other support by the back end and pupating. The ladybug pupa stage lasts about one week. Shortly after emerging from their pupae, which are black with red spots, adult ladybugs are ready to mate. Depending on food supply and extremes in temperature, ladybugs can alter their development or enter diapause until conditions are more favorable.
Convergent ladybugs (Hippodamia convergens) are found in woods, meadows and garden areas throughout North America. Aphids form the bulk of a convergent ladybug’s diet. Ladybugs cannot reproduce without feeding on aphids. When aphids are scarce, ladybugs will eat nectar, honeydew, pollen and soft plant parts.
Like all beetles, ladybugs have two pair of wings – hind wings folded under hard forewings (elytra), which protect the hind wings and the abdomen. Convergent ladybugs have red or orange elytra with six black spots on each – 12 total spots. The prothorax (area behind the head) is black with a white border and two convergent white lines.
Convergent ladybugs are solitary except when overwintering. In the western United States, huge accumulations or swarms of convergent ladybugs form and fly into mountain valleys where they overwinter for up to 9 months under leaves, logs or other litter. Upon emerging in the spring, the ladybugs immediately spread out in all directions in search of food before mating. The common name, convergent, refers, not to their swarm formation, but rather to the convergent white lines on the prothorax.
Convergent ladybug swarms are commercially collected while dormant during the winter, sold and freed near crops vulnerable to aphids for aphid control. Unfortunately this practice is usually considered a waste of time and money. When the ladybugs come out of dormancy they immediately migrate or spread out in all directions. This movement appears to be under genetic control By the time the ladybugs have fed and are ready to lay eggs, they have left the target area. Additionally, wild-harvested ladybugs carry parasites and pathogens which are moved to different areas. Therefore laboratory raised ladybugs, which have been specially treated to not migrate following dormancy and which do not have parasites and pathogens, are recommended for aphid control rather than wild-caught ladybugs.
These convergent ladybugs were accumulating at the University of California Botanical Gardens in Berkeley.