Introduced
Species Summary Project
Asian Ladybird
Beetle
Harmonia axyridis (Pallas)
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Common
Name: Asian Lady Beetle
(Multicolored Asian Ladybird Beetle, Asian Ladybug)
Scientific Name: Harmonia axyridis (Pallas)
Classification:
Phylum or
Division: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Coccinellidae
Subfamily: Coccinellinae
Identification:
Adults are 1/4 inch long; adult wing colors commonly range from red-to-mustard
in color with black spots ranging from zero up to 20 (typically 16 or
more). False, white, football-shaped
“eyes” behind the head are a key feature. Larvae have the “alligator-shape” of
other lady beetles and are black with orange streaks running along both sides
of the body. (Often mistaken for the seven-spotted lady beetle, which is often
found on the same hosts and plants.)
Original
Distribution: Southeast Asia
Current Distribution: By 1994,
the beetle was commonly found throughout the continental U.S. and Canada. It has also been intercepted on a plane full
of Christmas trees otherwise bound for Hawaii.
Site and
Date of Introduction: Between the late 1910’s and the mid-1970's, there
were several planned and accidental introductions to the U.S., with no
survival. Many planned releases across the eastern U.S. in the late 1970's and
early 1980's were attempts to use the beetles to help control aphids and
scales. After years without a sighting, the beetle was seen in Louisiana in
1988. Whether this final, successful
colonization was due to a planned release or an accidental introduction is
under debate.
Mode(s) of Introduction: Released
either by U.S.D.A. Agricultural Research Service or accidentally via a ship
from Asia.
Reason(s)
Why it has Become Established: Each female Asian Ladybird
Beetle lays 500-700 eggs; there are several generations per year and the
beetles live about three years. They have no native natural enemies and birds
assume from their warning coloration that they taste bad. They also play dead when in danger, and most
predators will not eat a “dead” insect.
Finally, their “bad smell,” produced possibly by a fluid in their leg
joints, drives predators away. The
larva is covered with bumps and spines and boasts sickle-shaped jaws that
produce a distinct bite. In addition to
appearance, the beetles have adapted to our climate quite well and can live in
trees and shrubs, fields, on beaches and in houses.
Ecological Role: The Asian Lady Beetle was
introduced as a biological control against crop pests. The larvae are larger
than most native ladybird larvae and both adults and larvae consume aphids. It
is a ravenous predator of arthropod pests such as aphids, mites, thrips, scale
and Lepidoptera eggs.
Benefit(s): The Asian
Ladybird Beetle is beneficial for most of the year; it has contributed to a
decrease in pesticide use on many crops and in orchards.
Threat(s): Asian Ladybird Beetles are
anecdotally suspected to be responsible for a decrease in the numbers of native
beneficial insects through predation and by elimination of scarce prey,
although this has not been scientifically proven. On a lesser “threat” level,
the beetles seek shelter for overwintering, and when a location is found, they
emit an "aggregating pheromone" to attract other beetles. Often, they choose a human home and gather
in the dozens, hundreds or thousands. They remain in that location through the
winter, annoying humans with their numbers, smell, and biting. The yellow, odorous defensive compound may
also stain furniture, carpets and draperies.
Control Level Diagnosis: Minimal
Priority, since they are clearly valuable as enemies of many pests,
although their possible cannibalism of other insects should be studied.
Control Method: Homeowners who have experienced an overabundance of
the beetles should seal up all the cracks in the foundation or siding of their
home. If they enter the home, the best option is to use black light traps at
night. They can also be gently vacuumed up using a less powerful vacuum. (The beetles should never be swept, since
the broom can rupture their bodies, and their blood smells). If the beetles are
trapped in a clean vacuum bag, they can be stored in a cool spot and released
in the spring.
References:
University of Georgia, Department
of Entomology (www.gaipm.org)
University of Florida, Department
of Entomology (www.creatures.ifas.ufl.edu).
Author: Stephanie
Taubman
Last Edited: 2/24/02
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Project Editor: James A. Danoff-Burg, Columbia University