Biology of the
Asian Lady Beetle
in South Dakota

Mike Catangui, Ph.D. - Assoc. Professor / Entomologist

The Asian lady beetle (Harmonia axyridis) has several common names:  Multicolored Asian lady beetle, Halloween lady beetle, and Japanese lady beetle.

Asian lady beetles are about 1/4-inch long and 3/16-inch wide.  Asian lady beetles can be distinguished from other lady beetles by the letter "M" marking on their thorax.  Although present in most specimens, this "M" marking may be absent in some individuals.  Counting the black spots on the wings is not a good way of identifying Asian lady beetles because they could vary from 0 to 19.  Variations in coloration and number of wing spots of Asian lady beetles collected from Minnehaha County can be seen in the image gallery.

Asian lady beetles are beneficial insects because they feed on aphids, scale insects, and other soft-bodied arthropods.  However, Asian lady beetles can become a nuisance in the fall because of their behavior of congregating inside homes in large numbers.  If disturbed or agitated, they may also excrete a yellow fluid that may stain carpets and walls.  

During the summer, Asian lady beetles may be found on plants where their preys (aphids and scale insects) also occur.  They may be found in trees, home vegetable gardens, ornamental plants, greenhouses, and in a variety of crop fields.  Eggs (yellow in color) are usually laid on the underside of plant leaves by the adult female.  Egg hatch occur within 3-5 days.  The larvae are highly mobile, elongate, and covered with tubercles.  Like the adults, these larvae actively seek and eat aphids and other soft bodied insects.  After about 2 weeks of feeding on their prey, the larvae metamorphose into immobile pupae, that will eventually turn into adult beetles after 5-6 days.  It takes about a month for an Asian lady beetle to develop from egg to adult.  Adult Asian lady beetles are known to live for as long as 3 years.

Asian lady beetles do not destroy wood or any structures in buildings, nor do they bite humans and pets.  They appear to enter buildings only for the purpose of seeking shelter.  Also, reproduction and feeding do not occur indoors.  Beetles that make it through the winter will leave their overwintering sites in early spring to start looking for prey and start reproducing in the field.

              References:   |  USDA-ARS  |   Ohio State University Fact Sheet HSE-1030-01  |