Ladybug Invasion (nature note)

My van has been invaded by the harlequin ladybird beetle (Harmonia axyridis).  That’s my favorite of its names.  Others include the Halloween ladybug (as they typically begin in late October to invade our homes in search of overwintering habitat) and the multicolored Asian lady beetle.  They may be red or orange with black spots, or black with red spots.

Because of this wide variation of coloration, they can be easily confused with our native species: the two spotted, nine spotted, and transverse ladybugs.  The simplest way to identify the harlequin is to look at its pronotom (the area between head and elytra [hard outer covering]).  If you spot the letter M (or W, depending on your perspective), it is the harlequin.

The harlequin was first introduced from east Asia to the USA in 1916 and is now considered to be one of the most invasive insects.  The hemolymph (the insect equivalent of blood) displays a broad-spectrum antimicrobial activity in human pathogens and, though this ladybird is quite successful in controlling aphids and scale insects, it can also be considered a pest for numerous reasons.

Harlequins call to one another with pheromones when they find a suitable place to overwinter and may gather in groups that number in the thousands.  They “reflex bleed” when agitated, releasing an unpleasant odor and hemolymph from their legs, and are known to bite humans when threatened.  They are tenacious little insects with good eyesight and will return to a favored spot no matter how many times you brush them away.  When they contaminate grapes, the taste of wine is altered.

This species is highly resistant to diseases that affect other ladybugs, and it carries a mircrosporidian parasite (to which it is immune) that can infect and kill other species.  Native species have experienced dramatic declines in areas where it thrives.