Applegater Spring 2012 11
Notes from a Rogue entomologist
Ladybugs: Lost and found
BY richArD j. hiLtoN
The other day my wife called out
to me from the kitchen, “There’s a lady
beetle in here.” Generally speaking,
a lady beetle in the house is not that
interesting—I was 99% sure that it would
be a Harmonia axyridis, the multicolored
Asian lady beetle, and indeed it was. As
the common name implies, Harmonia
has many different color forms, more than
any other lady beetle, and the number of
spots range from zero to more than 20. The
color of the beetle’s elytra, the hardened
forewings that act as a sort of shell, can be
bright orange or black. But the interesting
thing is that, when we moved here 25 years
ago, there were no Harmonia to be found
in southern Oregon or really anywhere else
in the United States for that matter.
What happened to change that state
of affairs is a story of good intentions gone
awry. As it turns out, two of the three
most common lady beetles in the country
are not native species. Besides Harmonia,
another introduced lady beetle found in
southern Oregon is the seven-spotted lady
beetle, also known as C-7 (an abbreviation
derived from its Latin name, Coccinella
septempunctata). Even though C-7 is rarely
seen indoors, they are very easy to find
outdoors and quite possibly even more
common than Harmonia. Both Harmonia
and C-7 were brought to the states to
combat pests, such as aphids and scale
insects, and they have done quite well for
themselves in North America.
Many of the crop pests that we have
in North America came here from other
parts of the world. When these plant-
feeding insects are transplanted to a new
region that does not have the naturally
occurring predators and parasites, the
populations can often reach very high
and very damaging levels. One way of
controlling these invasive pests is to bring
in predators and parasites from a pest’s
country of origin and release them. This
is known as classical biocontrol. When
this tactic is successful, it can be incredibly
cost-effective and can result in major
reductions in pesticide use. However, the
problem with this method of pest control is
that once the biological control agents are
released and established, there is no way to
put that genie back into the bottle. Now it
is the flourishing population of imported
ladybugs that pose a problem.
While these introduced lady beetles
do help to reduce pest populations,
there are downsides to this success. The
Harmonia population can become a
nuisance in the fall when they form large
congregations that seek out concealed
places to spend the winter. Nowadays,
the most readily available concealed places
are not caves or crevices, but garages and
attics. These masses of beetles can get active
Native species convergent lady beetle, left photo (www.dpughphoto.com/images),
and ashy grey lady beetle, right photo (www.whatsthatbug.com).
if they get warmed up to a sufficient
degree. It is not well-known that
ladybugs have defensive chemicals,
which they use to repel attackers.
A single ladybug might not have
a noticeable odor, but when you
get dozens or hundreds together,
they can smell very pungent and
unpleasant. Harmonia, sometimes
called “Halloween beetles” because
they show up in houses in the fall, are
also quite voracious and are known to bite
people who handle them. Once again, a
single ladybug bite is no big deal, but if you
are so unwise as to handle a mass of these
beetles, then the number of bites can cause
a certain amount of pain and discomfort.
Another problem associated
with Harmonia occurs when they are
inadvertently harvested with wine grapes.
When the grapes are crushed, the pungent
defense chemicals that the Harmonia
release can affect the flavor of the wine.
While one is tempted to joke about such
things, it is no laughing matter to either
the winemaker or the wine taster.
So, it began with the introduction
of aphids and other pests, which was then
followed by the introduction of nonnative
lady beetles, such as C-7 and Harmonia, in
order to control the pests. Ultimately, these
two species have become the dominant
lady beetles in many places throughout
the country, including southern Oregon.
You might think that there would be
enough aphids to go around, but when
species compete for the same niche, you
will often get a winner and a loser. Right
now, the invasive lady beetles, free of their
own parasites, have the upper hand, and
our natives, such as the convergent lady
beetle and the ashy gray lady beetle, have
become much less common.
If you want to help document the
population of our current ladybug species,
there is a website devoted to that task: the
Lost Ladybug Project (www.lostladybug.
org). You can send in pictures of ladybugs
Nonnative species Harmonia axyridis, top
photo (www.lternet.edu/gallery), and
C-7, bottom photo (www.dpughphoto.com).
that you find along with information about
the location where you found them, and
assistance is provided to identify the species.
This is a good example of “citizen science”
with the public contributing information
that a single researcher cannot readily
obtain, such as how ladybug populations
are changing across the continent.
So feel free to start hunting for lady
beetles, but don’t be surprised when our
native species prove hard to find.
Richard Hilton
541-772-5165
richard.hilton@oregonstate.edu
Senior Research Assistant/
Entomologist
Oregon State University
Southern Oregon Research and
Extension Center
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