Lost Ladybug Rediscovered
The puzzling demise of nine-spotted lady beetles took a new twist in 2006 when one of the insects was collected in an Arlington, Virginia home.
This was the first individual lady beetle of the species, Coccinella novemnotata, found in the eastern United States in 14 years.
Their absence nowadays is remarkable, since they used to be one of the most common native ladybugs around. They made up, for example, 20 percent of the lady beetles collected in Ontario corn fields in 1963. These colorful insects ranged across North America, from Maine to Washington state.
The decline of C9, as nine-spotted lady beetles are nick-named, was astonishingly swift. Before 1967 they appeared prevalent and widespread. By 1985, they were rare and by 1996 had all but vanished across the continent. A four-year search of Ontario corn patches from 1967 to 1970 found no C9s. Throughout the 1990s, searches for C9 turned up empty-handed in New York, New Brunswick and other eastern states and provinces.
The last records of C9 collections came from Maryland in 1986, Pennsylvania in 1987, Delaware in 1988 and Maine in 1992. The only known collections of C9 since 1996 were two individuals in Wisconsin in 2000 and four in Washington state in 2001, and now the one in Virginia.
Even more surprising, was that the disappearance was not of a creature with specialized habitat or prey needs, as is often the case for imperilled species. C9 could live nearly anywhere. It did well in farm fields of corn, potatoes, soybeans or alfalfa where it helpfully fed on aphids. It was also found abundant in red pine forests and amid weeds.
Why this ladybug suddenly died out, scientists have not been able to determine, and may never know. Climate change and shifts in land use, particularly reductions in farmland, are possible causes. The chief suspected culprit, though, is an introduced species.
Ladybugs from Eurasia were often released in North America to control aphids on agricultural crops. One of these, seven-spotted lady beetle, was introduced beginning in 1958 and by the early 1970s had established wild populations. That's about when C9 started becoming scarcer.
This new species, Coccinella septempunctata, flourished to became one of the most abundant introduced ladybugs in North America. It also happens to be C9's close relative, belonging to the same genus.
But scientists will only ever be able to speculate on what the implications of C. septempunctata's arrival were for C9's survival. Because population dynamics of the Coccinella lady beetles were never studied at the time, no scientifically-based conclusions on the matter can be made.
Jason P. Harmon, Erin Stephens and John Losey. 2007. The decline of native coccinellids (Coleoptera: Coccinellidae) in the United States and Canada. Journal of Insect Conservation. 11(1): 85-94.
John E. Losey, Jordan E. Perlman and E. Richard Hoebeke. 2007. Citizen scientist rediscovers rare nine-spotted lady beetle, Coccinella novemnotata, in eastern North America. Journal of Insect Conservation. 11(4): 415-417.