If you live in the USA, you are more likely to refer to lady beetles as ladybugs, but the obsessive taxonomist that lurks within all entomologists compels us to spoil your fun and remind you that “all bugs are insects, but not all insects are bugs”. In the UK, the more whimsical common term of “ladybird” is used, though the mediaeval Christian symbology conferred onto ladybirds provided additional common names such as the evocative but perplexing “God’s little cow”. Lady beetles continue to have a strong hold on modern minds; as a child, I remember an obligation to recite the ditty “ladybug, ladybug, fly away home, your house is on fire, your children are gone”, which with the bloody-mindedness of youth I never questioned (though I did wonder why lady beetles above all others of their kin were so doomed to flaming immolation).
The ability of lady beetle larvae and adults to consume large numbers of pest insects has given them an exalted status as biological control agents, but unfortunately, their appeal as beneficial insects has also led to the downfall of several of our native species. Many species from other countries have been imported for use as biocontrol agents against crop pests in North America. One of the best-known stories is that of the Vedalia Beetle (Rodolia cardinalis), a coccinellid brought in from Australia in the 1890s to control the cottony-cushion scale insect (Icerya purchasi) that was devastating California’s citrus crops. According to Marshall (2006), 179 species of lady beetle have been imported into North America as biological control agents, and several, along with additional unintentional imports, have become established. In my own garden, the native Convergent Lady Beetle (Hippodamia convergens), so-named for the angled white lines on the pronotum, is outnumbered by the Seven-Spotted Lady Beetle (Coccinella septempunctata), a European import; in the east, this species is thought to have largely ousted the native Nine-spotted Lady Beetle (C. novemnotata). And if there is one lady beetle that everyone loves to hate, it’s the imported Multicolored Asian Lady Beetle (Harmonia axyridis), which varies from pale orange to bight red, with many to no spots, but which can always be distinguished by the blotchy black “M” marking on its white pronotum. The Multicolored Asian Lady Beetle has an unfortunate tendency to invade people’s houses in the fall in search of hibernation sites, where the chemicals they secrete as a defense mechanism stain walls and furniture. During large outbreaks they may feed on and damage fruit crops such as grapes, a very un-lady(beetle)-like behavior, and when their secretions are left on grape skins they can cause an off-flavor in the resulting wine.