Invasion of the Ladybugs!

Jon Zawislak & Austin Jones

© Jacqui Geux, inaturalist.org (CC-BY)

Just in time for Halloween, an army of orange and black invaders may be creeping up on your neighborhood.  Each autumn, as the chilly weather settles in, so do the multi-colored Asian lady beetles.  This insect species sometimes likes to make itself at home… in your home.

What are lady beetles? 

Lady beetles, more commonly known as ladybugs, are members of the insect order Coleoptera and family Coccinellidae. While many people may refer to these insects as ladybugs, this common name is actually slightly askew from accuracy.  True “bugs” (like stink bugs and bed bugs) hail from the order Hemiptera.  Lady beetles were traditionally called ladybirds in medieval English as many farmers highly prized the insects’ pest-fighting predatory tactics and thought they had been sent from above by “Our Lady,” the Virgin Mary.  Thus, the common name for the group became ladybird beetles, or just lady beetles, and in the US, ladybug, because what is more fun to say than bug, right? 

There are nearly 500 species of lady beetles in North America, out of more than 6,000 around the world.  Some appear familiar, but many may not be recognized by a casual observer because they lack distinctive red-orange coloring and black spots.  However, the multi-colored Asian lady beetle lives up to its long common name.  It’s originally from Asia, but now occurs across the United States and around the world, and its color and markings are highly variable.  Their elytra (the hard, shiny wing covers) may be pale orange to a deep red-orange, and sport anywhere from 18 black spots to none at all.  Some beetles may also appear black with light or dark orange spots.  A feature they all share is a recognizable dark “W” shaped mark on their pale pronotum, the part of the exoskeleton between the head and the elytra. 

© Gavin Slater, inaturalist.org (CC-BY)

The scientific name for this beetle is, Harmonia axyridis, and it was purposefully imported and released in several countries as a beneficial predator with a voracious appetite for small, soft-bodied pests such as aphids, scale bugs, psyllids, adelgids and others.  Attempts to introduce these beetles in the U.S. go back as far as 1916, but the first stable populations were not recorded until 1988 near New Orleans.  They have been moved around the globe, both on purpose, and accidentally, and are now widespread throughout North and South America, Europe, Asia, Africa and New Zealand. Their spread has proved to be a mixed blessing.  While they do not harm plants or people, and have proved to be very helpful in controlling numerous farm and garden pests, they are often perceived as a nuisance in areas where introduced. 

While not originally from around these parts, this little critter has become one of the most common “ladybug” species the U.S., and in Arkansas.  Their big appetites and wide range of potential prey species has allowed these Asian lady beetles to adapt and thrive nearly everywhere they have found themselves, often at the expense of native species (about 20 of which are native to Arkansas), like the now imperiled 9-spotted lady beetle, the state insect of New York. 

Multi-colored Asian lady beetles have few natural enemies in the territories where they have spread, and most predators find them unappetizing.  When disturbed, lady beetles can secrete a foul-smelling liquid as a defense, and may even try to bite. Their high-visibility colors generally warn birds and other creatures that they would not make a good meal, as is the case with most lady beetle species.

Why do lady beetles come indoors? 

Image generated using OpenAI’s DALL·E 2

In their natural habitats, these beetles aggregate together in large numbers to overwinter.  When cool temperatures arrive, lady beetles begin to gather on sunny rock faces where they can soak up a few last warming rays and can easily find cracks and crevices in which to hunker down for the cold season.  In our climate, they are often observed to gather on the sunny sides of buildings and homes on bright fall afternoons, where they may seek to enter cracks beneath siding or between mortar joints, around door and window trim, or where utility pipes or wires enter walls.  Large hidden populations may lurk in dark, secluded areas inside of a home’s walls, attics or basements.  

Once inside their protective winter lairs, ladybird beetles like to hibernate until the warm spring sunshine draws them back out to play.  However, if they move into walls, they may only rest for a few weeks of brisk fall weather.  As outside temperatures drop and stay cold, people tend to turn up the heat indoors.  A toasty warm room can create a heat gradient inside the walls, causing the sleepy ladybirds to begin to stir.  They will then creep towards the warmth, assuming they are heading outside, and can begin to emerge from crevices inside of a home, around window trim or electrical outlets and light fixtures.  They may be found in groups, in corners or on windowsills, trying to figure out where they are.

Should I be worried?

Lady beetles can bite if handled without care or if they feel threatened.  This may be felt as a pinch and cause a tiny welt, but won’t cause any permanent harm.  If disturbed, they may release their stinky defensive ooze, which can stain drapes, carpets or other fabrics.  These same compounds can make pets sick if eaten in large enough numbers by a curious dog, but will not be fatal.  In extreme cases, some highly sensitive people may have an allergic reaction to these defensive fluids, resulting in dermatitis or a stinging sensation.  However, lady beetles do not damage structures, chew or bore holes in walls, or consume stored products, furniture, or clothing.  They also do not lay eggs inside of homes.

What can I do about lady beetles indoors?

The most effective way to manage lady beetle invasions is to exclude them from a structure in the first place.  Sealing cracks and crevices on a home’s exterior will do more to control pests than any amount of insecticides.  Prevention is the best defense. Inspect your home, sealing with caulking and other products where appropriate, before any insects begin can move in. 

If lady beetles do get inside, use a vacuum cleaner to quickly pick them up, but be sure to dispose of the vacuum bag immediately outdoors, before they begin escaping from your vacuum cleaner.  If you prefer to catch-and-release these beneficial garden friends, place a nylon stocking into a vacuum extension, secured with a rubber band on the outside.  Once the beetles have been collected, take the stocking outside and turn it inside-out to release them into the wild again, away from your home.  You could even keep them in a container, with air holes and a damp towel, in an unheated space (like a garage or shed) to allow them to hibernate until you release them into your gardens again in the spring. 

Pesticides are not recommended for lady beetle control.  Only products labeled for indoor use should be applied inside any structure, but even use of these can cause dead beetles to accumulate in large numbers inside wall voids or under floors, which can lead to an unpleasant odor, as well as attract other scavenging insects to feed on them.

Visit our webpage on multi-colored Asian lady beetles for more specific management tips.