Friday, November 2, 2007
By and large, people have a great fondness for ladybugs but the goodwill goes out the window as the Asian ladybugs come in. Around this time of year, the pumpkin-colored insect comes into buildings through any opening including tiny cracks and crevices and congregates with hundreds or thousands of its kind looking for shelter for the winter.
Name. Ladybugs and ladybirds are actually beetles; they are members of the beetle family, Coccinellidae. More than 480 species are found in North America. The Asian ladybug is Harmonia axyridis and is also known as the Asian multicolored ladybug (since there is a lot of variation in color and markings) and the Halloween ladybug (since we most often see it in October and it wears the orange and black colors associated with Halloween).
When and where seen. For about two weeks now the Asian ladybug has been showing up in and on houses all around Carlisle, generally on sunny south-facing walls. I have a few dozen on my side porch and have seen dozens more crawling on the front of the house looking for a way in.
Department of Agriculture. The U.S. Department of Agriculture (USDA) introduced the Asian ladybug to California first in 1916 and again in 1964 and 1965 to do agricultural work, mainly in apple and pecan orchards. It gets no pay but all the food it can eat and it takes on work that few others want eating aphids, scale insects and mites. The USDA also introduced it in various eastern states starting in 1972. An inadvertent introduction in Louisiana in 1988, probably from cargo unloaded at the New Orleans port, also seems to have contributed to the insect's becoming established across most of the United States.
Department of Defense. Thomas Eisner is an entomologist who, like the elephant's child, has an insatiable curiosity. (He is also a fine author and I recommend his book For Love of Insects to anyone similarly afflicted.) His curiosity about defense mechanisms of ladybug larvae led him to conduct a simple but interesting experiment. Ladybug larvae are quite conspicuous and therefore need some kind of protection from predators. He thought that if he simulated the touch of an ant antenna by stroking a larva gently with a brush, it might mistake him for an ant and do something defensive. He discovered that the larva used the gaps between the segments of its abdomen like a row of traps. By flexing the abdomen, the larva closed the gaps and "bit" the virtual ant. Eisner confirmed this behavior with real ants, and any that were pinched fled. He doesn't say if they left behind any body parts. Adult ladybugs, including the Asian immigrant, defend themselves by "reflex bleeding," which is the secretion of sticky, yellow, foul-smelling blood from their knee joints. The adults are also reputed to bite, but I have yet to experience this, and I have provided plenty of opportunity.
Distinguishing characteristics. The best way to identify the Asian ladybug is by its home invasion behavior in the fall. Native ladybugs don't do this. The Asian ladybug is a tree-dwelling species so we don't see it often during the summer and anyway it would be hard to identify since it could be yellow, orange, or red and could have as many as 19 spots. The spots can sometimes be so pale as to be almost non-existent. The Kaufman guide warns against trying to identify any ladybugs by color and pattern alone.
Ladybugs in the house. Asian ladybugs can be a pest if too many of them invade your home. Don't squish them or swat them because the reflex bleeding will be smelly and will stain. Ohio State University suggests replacing your vacuum cleaner bag with a knee-high stocking and vacuuming them up into this convenient container. You can then release them in the spring. If you decide to leave them alone, they won't lay eggs in the house, and they won't get into food. They will cluster together in a darkened corner and hibernate until spring when they will attempt to get out. All the sources I found said the best way to deal with them is to seal the cracks they use to get in.
Did you know? The ladybug is the state insect of Massachusetts. The particular species of ladybug is not named but it is probably the two-spotted ladybug, Adalia bipunctata.
Sources. Field Guide to Insects of North America, Eric R. Eaton and Kenn Kaufman; For Love of Insects, Thomas Eisner; Agriculture Research Service of USDA at www.ars.usda.gov/is/br/lbeetle/; Ohio State University Extension at http://ohioline.osu.edu/hse-fact/1030.html.
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© 2007 The Carlisle Mosquito