04-05-06 and the multicolored Asian lady beetle

On the first Wednesday of April, at a very early hour in the morning, the time and date were 01:02:03 04/05/06--a unique numerical alignment only to be experienced once during this century. Of course, I slept right through this fleeting, historical (and trivial) second. But later in the day, I was walking across campus at 1:02:03 in the afternoon and reflecting (but not too deeply) on the moment, and that if I didn't use military time (and I don't), then this experience should be just as valid at the nighttime numerical alignment. Viola! I had witnessed history, but I was soon distracted by insects. Buzzing back and forth in the sunshine and landing on people walking along the sidewalk were multicolored Asian lady beetles. The sight of the lady beetles combined with the numerical "thing" reminded me of a question that many farmers and crop specialists had asked during the last several years, "Have these lady beetles always been in Iowa, and if not, where did they come from?"

So I did some searching and found a great article that summarizes the biology and impacts of the multicolored Asian lady beetle. It was written by Robert Koch, University of Minnesota, and most of the information below comes from his article The multicolored Asian lady beetle, Harmonia axyridis: A review of its biology, uses in biological control, and non-target impacts. Here are some facts that I found interesting.

Name: Multicolored Asian lady beetle, Harmonia axyridis. The common name was approved by the Entomological Society of America for use in their publications.

Color: Wing covers range from yellow-orange to red with zero to 19 black spots, or may be black with red spots.

Original distribution: China, Japan, Siberia.

Life history: Eating a diet of pea aphids at a constant 79 °F, the average duration of each stage was: egg 2.8 days, first instar 2.5 days, second instar 1.5 days, third instar 1.8 days, fourth instar 4.4 days, and pupa 4.5 days. Adults typically live 30 to 90 days, but they are recorded as living up to three years. Under laboratory conditions, females have produced 3,819 eggs at a rate of 25.1 eggs per day. However, another report gives the maximum fecundity as 1,642 eggs.

Supercooling point: -2 °F (temperature at which adults freeze and die).

Population dynamics: Cannibalism plays a role in influencing the population. About 50 percent of eggs are eaten by larvae, while mortality within the fourth instar (93.3%) was the highest of all life stages, due to a food shortage after aphid populations crashed. Survival from egg to adult may range from 0 to 16 percent.

Aphid consumption: The total number of aphids consumed through the larval stages varied from 90 to 370 aphids, depending on the species, and across all larval stages averaged 23.3 aphids consumed per day. Adult consumption typically ranges from 15 to 65 aphids per day, again depending on aphid species.

Defense: Adults are aposematically colored (meaning their color serves as a warning) and when attacked, will secrete alkaloid-laden "blood" from their leg joints. This behavior is known as reflex bleeding. The "blood" is bitter to the taste (speaking from personal experience).

Establishment in the United States: This lady beetle was extensively released for biological control of other insects, beginning in 1916 in California. During 1978-1981, the beetle was additionally released by state and federal (USDA) agencies in several states along the Atlantic Coast and Gulf of Mexico. Accidental entries have arrived on nursery stock at ports in Delaware and South Carolina. The first extensive populations were not found in the United States until 1988 near the port of New Orleans, Louisiana. Therefore, it is not known for certain whether the lady beetles' establishment in the United States was the result of accidental entries, planned releases, or both.

Iowa status: The multicolored Asian lady beetle was never released by Iowa State University in Iowa. The population we have is the result of the beetles probably flying here from Louisiana, or hitchhiking in a vehicle, although we will never know for sure how they arrived. They were first reported in Iowa in 1994. It is now a permanent, although sometimes unwanted, resident of our state. It is a known predator of the soybean aphid, and in that sense, it is a beneficial insect. However, it has become a serious pest in Iowa vineyards--the alkaloids from a single beetle crushed in a cluster of grapes can ruin large quantities of juice, resulting in off-flavor wine. And if you live in a house in Iowa, you probably appreciate the nuisance factor of these little beetles during October when they defy all our efforts to keep them out and off our walls.

Insects and time--who can stop either one?

Mass of Asian lady beetles
A mass of multicolored Asian lady beetles preparing to hibernate for the winter. (Marlin E. Rice)

This article originally appeared on pages 84-85 of the IC-496 (6) -- April 10, 2006 issue.

Updated 11/09/2006 - 9:44am