Lady Beetle: Friend or Foe?

Asian Lady Beetle (Harmonia axyridis)

July 5, 2013

As the weather has been warming up (quite rapidly!) this spring and early summer, have you noticed any ladybugs waking up inside your house? Have you vacuumed what seems like thousands of them out of your windows? Have you dealt with the stink they make when squashed? If so, you may be suffering from a ladybug infestation in your house, and you probably loathe these little critters. But, did you know the Asian Lady Beetle (Harmonia axyridis) was originally introduced into the United States as early as 1916 as a beneficial insect and biocontrol agent?

The first controlled introductions of lady beetles took place in the early 1900s as a means of naturally controlling damaging pests in crops such as alfalfa, pecans, and citrus fruits. The species repeatedly failed to establish themselves in the wild, though, despite subsequent introductions. An established population was discovered in Louisiana in 1988.  In the next few years it spread quickly to other states, being observed occasionally in the midwest, and it was common in the midwest by 2000. The USDA, Forestry Commission, states, and private agencies have continued to release Asian Lady Beetles in the last 15 years, and many feel this beneficial insect has been useful in reducing the need for pesticides, though at this time they are no longer being released. They have also helped rid hardwood forests of disease-carrying aphids, mites, and scale insects.

These critters do seek shelter when the weather turns in the fall, though, earning them the name of the Halloween lady beetle. If you have them in your home, rest assured that research entomologists have been working on methods to prevent these ladybugs from invading your home as well as ways to effectively capture them once inside. The most recommended method at the present is to caulk cracks around doors and windows and replace or repair damaged siding. Fortunately, these critters only seek shelter in your home, they do not lay eggs inside or feed on home materials – they are not structure damaging insects. And that smell the release when you squash them? That comes from “reflex bleeding” when a stressed ladybug releases a smelly, yellow fluid from its joints. The best way to remove them from your home is by vacuuming them up rather than squashing them.

We have been lucky enough to not find them in the 1900 house, but I’ve gotten a few pictures of the life stages of this ladybug on the cherry trees in the orchard and around the garden in the past few weeks. The Asian Lady Beetle goes through four life stages, similar to a butterfly. The adult female lays eggs on the underside of leaves near aphid colonies – where she’s sure her offspring will have plenty to eat.

The larva hatch in 3-7 days and look like little alligators voraciously hunting for food. If you see these strange looking critters on your plants in late spring, leave them be! They have an incredible appetite for damaging pests and no taste for your garden greens.

Asian Lady Beetle larva looking for aphids on the cherry tree

The larva molt a few times before attaching themselves to a leaf. They are now in the pupa stage where metamorphosis takes place – just like a caterpillar in a cocoon – soon an adult ladybug will emerge.

Asian Lady Beetle pupa

The length of time for metamorphosis to occur depends on environmental factors, but once it is complete, a vulnerable adult ladybug emerges and waits for its exoskeleton to harden. They often look shiny, wet, and pale upon first emerging. The exoskeleton hardens in a few hours, and pigments develop giving them a rich red, orange, yellow, or pink pigment. Markings range from many black spots to no spots – even some melanic varieties that are black with two or four red spots. White markings always define an “M” shaped black area on the head. The many colors this beetle exhibits have given it the colloquial name of Harlequin Ladybug.

the many colors of the Asian Lady Beetle

Try to remember that while the October swarms and stinky bugs in your house might be obnoxious, these tiny guys are aphid-hungry and are very beneficial insects to farmers, gardeners, and horticulturists alike!

Facts about the Asian Lady Beetle

Written by Kelly Clime, 1900 Farm Manager

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Animals in Action   How Does Your Garden Grow   Science of Everyday Life