What
is the correct name of this insect?
You will hear several versions of the common name of this insect. It has
been called the multi-colored Asian ladybird beetle, multi-colored Asian
ladybug, Asian lady beetle and even the Halloween beetle. The name we
are most familiar with is multi-colored Asian lady beetle. The scientific
name of this insect is Harmonia axyridis. It only has one of these!
Every
time I read something about ladybugs the author always mentions their
importance for controlling aphids. What's an aphid and why is it so important
to control them?
The insect group we call aphids, (also called
plant lice) is a large group of small (fruit fly-size), soft-bodied insects
that are often found in large numbers sucking the sap from stems or leaves
of plants. They feed in colonies that often contain large numbers of individuals.
When aphids feed, they damage plant tissue creating a loss of plant fluids
and the photosynthetic tissue needed to produce energy for plant growth.
Over time, this causes loss of plant vigor. Aphids also transmit many
plant diseases. Ladybugs are efficient and effective predators of aphids
of all kinds. This is especially important to farmers as loss of plant
vigor in their crop means a smaller harvest. The presence of a ladybug
population effectively controlling aphids means less insecticide use and
a greater profit after harvest.
How
can I tell a multi-colored Asian lady beetle apart from the ladybugs (or
lady beetles) most of us are familiar with in Michigan?
This can be a little confusing because multi-colored Asian lady beetles
are highly variable. While they all have the same shape they do not all
share the same coloration and pattern of black dot marks. The color of
their wing covers range from pumpkin-orange to mustard-yellow and even
jet-black. They may have no black spots or as many as 20 of the ebony
polka dots. In Michigan, the vast majority seem to be mustard-yellow and
the number of spots range from zero to eighteen. Despite the wide variation
in background color and number of spots, they all share a distinguishing
mark on their pronotum. Viewing the beetle from it's topside, the pronotum
is that small section that separates the head area from the abdomen (where
the wing covers start). There is a mark on the pronotum that looks like
a "W" or "M" depending upon whether you are looking
at it from the front or rear. All multi-colored Asian lady beetles have
this mark that domestic ladybugs lack.
Where
did the multi-colored Asian lady beetle come from?
This insect is native to northeastern Asia.
How
did this insect find it's way to Michigan?
There is some confusion about this issue. There are records of attempts
to establish this insect in the U.S. as far back as 1916. In the early
1980's the United States Department of Agriculture experimented with this
insect in the southeast U.S. They were trying to establish it as a predator
against aphids and other soft-bodied pests of pecan trees, a valuable
nut crop. According to USDA scientists, they were unsuccessful in their
attempt to establish the beetle. However, in 1988 an established population
was discovered in Louisiana, near New Orleans. The multi-colored Asian
lady beetle was first officially reported in Michigan in 1994 but has
probably been present since the early 1990's. Today, it can probably be
found in all 83 Michigan counties and several other states.
Why
do so many multi-colored Asian lady beetles show up in and on my house
in the fall and sometimes -- lasting right into spring?
In the fall of the year, multi-colored Asian lady beetles begin to seek
out cavities where they will spend the winter hibernating. They require
cavities that will stay cool and dry and offer concealment. Throughout
their native range in Asia, the adult beetles seek out cavities in cliff
faces and other naturally occurring cool, dry cavities. In our part of
the world, they have found equivalent winter quarters in the exterior
of buildings. They are most commonly found gathering in the fall on the
sun-facing exposure of the building --usually a southern exposure. This
activity often results in the beetles getting into the inhabited portions
of the building. In the spring, they will all leave.
If
the multi-colored Asian lady beetle hibernates all winter, why do I get
them in my house in the winter?
Even on cold winter days there are often times when the wind is calm and
it is sunny. On these days (especially later in the winter when days grow
longer), there is sufficient radiant energy on sunny exposures (especially
southern exposures) to warm the siding. If the temperatures where the
beetles are hibernating get near 50 degrees F, some beetles will wake
up and begin crawling around. Some or many will then find their way into
inhabited areas of the house.
When
they get into the house during the winter, I see many of them gathered
on and around windows, but for the life of me, I cannot find any cracks
or gaps around the windows where they may have gotten into the house.
How can this be?
These insects are photopositive -- they move toward the light or towards
the window in this case. Insects also have very small brains. They can't
figure out glass and why they can see the outdoors, but can't get there!
They have found their way into living areas by other routes and have only
ended up on the window.
A
friend of mine told me that these beetles were introduced by the DNR to
control gypsy moths. Is that true?
No. To our knowledge, no intentional releases of multi-colored Asian lady
beetles ever occured in Michigan.
What
good do these beetles do, if any?
Ladybugs, in general, actively prey on aphids and other soft-bodied insect
plant pests. Both adults and immature multi-colored Asian lady beetles
kill significant numbers on these plant pests, especially aphids. Additionally,
the multi-colored Asian lady beetle aggressively pursues these plant pests
that attack trees; more so than our native ladybugs. In 2000, the soybean
aphid, an exotic aphid from China, was discovered feeding on soybean plants.
In 2001, the multi-colored Asian lady beetle fed heavily on the soybean
aphids and likely saved Michigan soybean farmers millions of dollars in
harvest revenues and insecticides that didn't have to be used to control
losses to this aphid species.
In
the fall, I see Asian lady beetles feeding on ripe fruit. I thought they
were predators?
Even a grizzly bear doesn't eat meat all the time. The multi-colored Asian
lady beetle is no different. As the growing season wanes, so does the
availability of prey. It is not uncommon to find these beetles looking
for sugar-laden fruit at this time of year.
I
had one of these beetles crawling around on my arm, and I think it bit
me. Do they all bite?
Some bite, most
do not. Sometimes the Asian lady beetles bite skin, but often this stinging
sensation is actually caused by small spurs on the beetle's legs pricking
skin as they move and evaluate whether or not the skin is a food source.
The beetle does not carry disease nor does it have any toxin associated
with its mouthparts. In most cases, the pain is short lived. If the bite
concerns you, apply antiseptic to the site.
I
heard that if you crush one of these beetles or have enough of them inside
your home they give off an unpleasant odor. Is that true?
When multi-colored Asian lady beetles are agitated they give off a yellowish
fluid that has a faint, foul odor. This is a defensive reaction to ward
off predators. It is called "reflex bleeding." The liquid is
exuded from its legs and it can stain.
Could
I be allergic to the multi-colored Asian lady beetle?
Yes, it is possible to have an allergic reaction to the multi-colored
Asian lady beetle. Prolonged exposure to infestations has been reported
to cause allergic reactions in some humans (Yarbrough et al 1999, mangnan
et al. 2002). Patients have described itchy nose and eyes, sneezing, upper
respiratory symptoms, and severe, persistant asthma. Here are some references
about research in this area:
Magnan EM; Sanchez
H; Luskin AT; Bush RK. 2002. Multicolored Asian lady beetle (Harmonia
axyridis) sensitivity. Journal of Allergy and Clinical Immunology,
Volume 109, Issue 1, pp 205
http://www2.us.elsevierhealth.com/scripts/om.dll/serve?action=searchDB&searchDBfor=art&art
Type=misc&id=jai021091ab0010205 (free access to abstract)
Yarbrough, JA MD,
Jack L. Armstrong, MD, Michael Z. Blumberg, MD, Amy E. Phillips, BS, Edna
McGahee, RN, William K. Dolen, MD. Allergic rhinoconjunctivitis caused
by Harmonia axyridis (Asian lady beetle, Japanese lady beetle,
or lady bug) Journal of Allergy and Clinical Immunology September 1999,
part 1, Volume 104, Number 3, p704 to p 705
http://www2.us.elsevierhealth.com/scripts/om.dll/serve?action=searchDB&searchdbfor=home&id=ai
(Paid access only to article).
Can
we expect large numbers of multi-colored lady beetles every fall trying
to get into the house?
Probably not. The number of predators is pretty much regulated by prey
availability. There are other variables including disease and climatic
conditions. The multi-colored Asian lady beetle population will rise and
fall with that of the insects they prey upon, especially aphids.
Do
they cause any damage to the house, get into food, that sort of thing?
Multi-colored Asian lady beetles are harmless. They cause no harm to a
building or its contents, including people and pets. However, when they
show up inside the house by the dozens or hundreds, they usually wear
out their welcome.
Where
do these beetles go in the spring?
As soon as the weather warms in the spring, the multi-colored
Asian lady beetles begin emerging from their winter quarters. They will
continue to do this until they have all departed for the season. After
they leave, they will look for food, mate and the females will begin laying
eggs on foliage. A short time later both males and females will die.
What can I do to control them around the house, and, better yet, keep
them out of the house in the first place?
Even though there are measures that can be taken to eliminate the beetles
as they appear in the house, the long-term solution to eliminating your
beetle "problem" in the house is prevention.
Outdoors preventative
tactics
Beginning in the early fall, monitor the sunlit side of your buildings
for swarming beetles. These are areas where they will collect prior to
moving into hibernation sites. You can apply an insecticide registered
for outdoor use. If it is practical, caulk obvious cracks and spaces where
the beetles can gain access, check attic vent screens and repair if necessary,
caulk wherever a pipe, conduit, telephone or cable TV wire goes through
the siding, and ensure that the weather seal on basement windows is tight.
Indoors preventative
tactics
Making the effort to eliminate points of entry from the outside into hibernating
areas is helpful. The real key to prevention is to also conduct the same
inspection on the inside walls and make repairs, where necessary. After
all, you probably wouldn't care how many multi-colored Asian lady beetles
were hibernating under your siding, in your walls voids and attic if none
of them entered your living space. Pay close attention and caulk all those
places where pipes, conduits and wires come through the walls. You can
use an insecticide indoors, but we don't recommend it. Why? One of the
biggest reasons is that the weather outdoors is still cool or cold and
the furnace is running. That means the house is closed up and the insecticide
is being re-circulated throughout the home -- probably not a good idea.
Additionally, when the bugs you have sprayed die, you will have to clean
them up anyway. That is why we suggest using a vacuum to eliminate the
beetles. A dust buster-type vacuum is ideal because it has a bag that
can be emptied.
I've
had it with these bugs! If they show up again in my house I'm going to
call the exterminator and be done with it. What do you think about that?
That is certainly another option. However, pest control businesses are
usually reluctant to treat for multi-colored Asian lady beetles in the
living quarters. Probably the main reason is that they cannot guarantee
their elimination for any length of time. They are able to kill the beetles
wandering around when they are treating, but have no practical, cost-
effective method of getting to areas where the hibernating beetles have
massed.
If
I discover where the beetles are hibernating in the wall voids, will household
insecticides kill them all?
You probably won't kill very many at all. Why? If you live in Michigan
and you discover hibernating beetles, it means that it is either late
fall, winter or early spring, at the latest. At this time the insect's
physiological activity is near nil and the chemical activity of the insecticide
is near nil also because of the low temperatures.