On a long-awaited sunny spring morning a week ago, when the air temperature finally bested 70 degrees, I was treated to a flurry of small insects filling the air in my backyard. Suspecting a termite swarm, it didn’t take long for me to discover the source of these aerial voyagers. The wooden risers of some garden steps apparently are home to a massive termite colony. Over the next several hours thousands of adult reproductive termites issued forth and took wing, off to found colonies of their own. We met tropical termites in previous episodes of Bug of the Week, but Eastern subterranean termites are the common ones found in the DMV.
Who’s filling the air around my home on a sunny spring morning? Why, thousands of reproductive termites spawned from wooden steps in my backyard. Watch as they issue forth from gaps in the wood and mount vegetation to take flight. Can you count how many there are?
Remarkable creatures, termites have the ability to perform a digestive magic trick unparalleled in the human world. They consume wood. To utilize nutrients tied up in a biopolymer hard enough to dull an axe blade, most termites rely on symbiotic bacteria in their gut to digest the rugged plant material called cellulose. Some primitive species of termites enlist unicellular organisms called protozoa to accomplish this feat. Termites have an unusual and rather crude way of passing these vital microbes from one termite to the next. They employ a process known as proctodeal trophallaxis. One termite excretes a droplet of microbe-packed fluid from its anus. This packet of goodies is consumed by another termite waiting at the rear end. Yum! In addition to the transfer of vital symbionts from one termite to the next, trophallaxis is also a way of disseminating chemical messages called pheromones that regulate the development and behavior of termites within the colony.
Termites are part of an elite group of social insects that include ants, bumble bees, honey bees, and yellow jackets we met in previous episodes of Bug of the Week. Social insects such as termites have a distinct division of labor with a caste system that includes specialized workers, soldiers, and reproductives. Workers are the most common caste in the subterranean termite colony. The primary tasks of these cream colored laborers is to consume and process wood, seek new resources, construct galleries and foraging tubes, and care for the young and reproductives. As the name implies, soldiers are tasked with colony defense. They are easily recognized by their enlarged heads with powerful darkened jaws. Depending on the species, soldiers are armed with jaws that stab, cut, or snap and whack an enemy. Termite reproductives are called kings and queens. As light colored juveniles in the colony, they pass through a developmental stage called the nymph and are distinguished from workers by developing wing buds found on the thorax just behind the head. When they molt to the adult stage, to become males (kings) and females (queens) their cuticle tans to dark black. This tanning process allows them to retain body moisture as they exit the damp earth and enter the drier world above ground.
Under a nearby piece of firewood, cream-colored workers begin to make galleries and remove wood in a fresh log. They disappear into subterranean crypts of their colony when exposed to daylight.
During spring and summer in Maryland, the air can be filled with thousands of reproductive, known as primary reproductives, swarming to found new colonies. But the world above ground is treacherous and only a few of the thousands that emerge live to establish a new colony. After landing at a new site, wings are no longer needed and kings and queens will quickly shed their wings by snapping them off with quick twists and turns of their body. Hopeful males frantically pursue potential mates and the lucky ones that succeed in the mating game help their queen establish a colony. Queens of some species may live more than 40 years and produce more than 20,000 eggs per day. Eggs hatch and develop into workers, soldiers, and new reproductives. In addition to primary reproductives, termite colonies may also contain light colored secondary reproductives lacking wings that develop directly from nymphs, and tertiary reproductives that develop directly from workers. This remarkable system of reproductive redundancy undoubtedly contributes to the longevity and success of a termite colony.
After taking flight and landing at a new colony site, a female termite snaps-off her wings, and is quickly pursued by a hopeful suitor.
In the natural world, termites live in subterranean nests, foraging on fallen trees. But with the advent of domestic structures they often colonize dark interiors of floor joists and paneling within our home if conditions of moisture and temperatures suffice. They reach the structural wood of our buildings by constructing tunnels of soil, wood, saliva, and excrement from an outdoor colony like the one in my flower bed, up foundation walls until they reach the wood of a sill plate or floor joist. There they enter the home. If wood is sufficiently moist, let’s say due to a leaky pipe, plugged gutter, or cracked foundation, termites can set up shop inside your home. The appearance of swarming winged primary reproductives inside your home is a sure fire indication of an infestation. To learn more about the biology and management of termites in and around your home, please visit the following excellent website:
Two great books, "The Insect Societies" by E.O. Wilson and “For Love of Insects” by T. Eisner, were used as references for this Bug of the Week. Bug of the week thanks Drs. Barbara Thorne and Nancy Breisch for assistance in creating this episode. All images and videos at Bug of the Week are copyrighted and may not be reproduced without permission.