Boxelder Bugs

     On a pleasantly cool, sunny afternoon in October of last year, I was walking through a long, thin woods of colored leaves along a creek in Lancaster County, Pennsylvania.  The dominant trees along that waterway are sycamores, black walnuts, silver maples, and ash-leafed maples or box elders.  I suddenly came upon a large, still gathering of attractive insects clustered tightly together on the sunny side of a large silver maple.  They were thousands of female eastern box elder bugs, each one of them about a half inch long and dark with striking, reddish-orange markings.  Those bugs, being cold-blooded,  as all insects are, were staying warm in the sunlight, but would soon retreat into crannies under loose bark and crevices in the wood of the tree for the cool night.  Eventually, as the fall weather continues to get cooler, these female box elder bugs will stay in their protective retreats for the winter and we won't see them again until the next spring.
     Many of us call all insects "bugs", but only the family of insects eastern box elder bugs belong to are truly bugs.  But the interesting box elder bugs inhabit bottomland, deciduous woods east of the Rocky Mountains, habitats where ash-leafed maples, their major food source, are common.  And every October, when the amount of daylight each succeeding day is less and average temperatures continually drop, fertilized female box elder bugs, sensing the approach of winter, come together in spectacular swarms at tree trunks with cavities, fallen logs, rock walls and the walls of barns, houses and other buildings.  They congregate almost wherever they can find protective crevices to slip into for the winter.  But,  although they don't bite or sting, nor eat anything through winter, most people don't like them around their homes, either outside or inside.  Just the sheer numbers of box elder bugs are what those folks don't like.  And some box elder bugs do enter homes by slipping under windows or through cracks anywhere in the walls.  Being in the warmth of a house, however, is detrimental to these true bugs.  Their metabolism is much higher in warmth and they run out of energy and die before winter is over.  They don't get to lay eggs in spring.  But box elder bugs in cold shelters retain energy to well into spring.  They get to lay eggs and pass along their genetic codes.  
     Those same female box elder bugs emerge from their dormancy in sheltered places late in spring and lay eggs in bark crevices or on maple leaves, then die.  Some of those eggs are eaten by a variety of small birds, including chickadees, kinglets, gnatcatchers, warblers and other species.  Surviving box elder nymphs hatch in early summer and are red.  Again some of them are eaten by a diversity of small birds.  But survivors gradually become dark with red trim as they grow.  Those nymphs ingest the juice of ash-leafed maple leaves along the waterways where that species of tree prevails.
     Upon maturity late in summer, male and female box elder bugs come together for mating; then the males die.  And only the females survive to overwinter to the next spring, when they carry on their species.  
     Female eastern box elder bugs congregate in sheltered retreats in October to pass the winter in comparative safety.  Some readers might be lucky enough to experience one or more of those swarms on a sunny, October day.  The bugs are attractive and don't cause any harm to people or their possessions.  And they are a major, interesting part of natural happenings in autumn in the United States east of the Rocky Mountains.  Their great congregations are another sign of fall.