Ladybugs, also called lady beetles or ladybird beetles, are actually beetles in the Coleoptera family Coccinellidae. As insects go, they are a very beneficial group, being natural enemies of many agricultural pests, especially aphids and other critters that damage plants by feeding on their sap. A single ladybug can consume vast quantities of aphids in its lifetime, perhaps as many as 5,000 or more.
There is a brisk business in commercial ladybugs for aphid control, and some of the species found here in North America are actually "invasives" brought from Europe or Asia for such purpose. Coccinella septempunctata, the seven-spotted ladybug, sometimes called ‘C-7', is a medium-sized, orange beetle with seven black spots. It is a European species that was introduced into the US to aid in managing some aphid pests.
The subject of this page was imported into North America many times
as a biological control vector, finally taking hold in the east
during the 1980's. It has been slowly
spreading across the country ever since. Asian lady beetles now rival the box elder bug for most annoying insect pest trying to get in my house to spend the winter.
I've seen then congregate in the thousands in outbuildings and
protected places outdoors, where the mass undergoes diapause. And
they bite. I've been bitten many times by these bastards, and it can
be painful. You can smack them and they get up and fly away! Such
nerve.
Despite these annoying traits, Harmonia axyridis is of great benefit to agriculture, preying as it does upon many species of
plant-injurious soft-bodied insects such as aphids, scales, and psyllids.
Seven-spotted Ladybug - Coccinella septempunctata attacks aphids feeding on goldenrod. |
Adult ladybugs have convex, hemispherical shaped elytra (the
hardened wings used to cover the soft flying wings underneath) that
can be yellow, pink, orange, red, or black, and usually are marked
with distinct spots. This is a type of warning coloration
(aposematic coloring), thought to discourage predators. Lady beetles
also have another defense: an odorous, noxious fluid that seeps out
of their leg joints when the insects are disturbed.
Ladybugs, both adults and larvae, are known primarily as predators of aphids (plant lice), but they prey also on many other pests such as soft-scale insects, mealybugs, spider mites and eggs of the Colorado Potato Beetle and European Corn Borer. A few feed on plant and pollen mildews. One larva will eat about 400 medium-size aphids during its development to the pupal stage. An adult will eat about 300 medium-size aphids before it lays eggs. About three to ten aphids are eaten for each egg the beetle lays. |
