St. John USVI Fauna: Termites
Have you ever closely observed the tree-dwelling termites that live in those giant dark-brown, elliptical nests? The scientific name of these creatures is Nasutitermes. On St. John they are commonly called wood lice or wood ants or simply termites. Our Latin friends call them comejen and down island they're known as pul bois. (Another species, called subterranean termites, also inhabits St. John, but their nests are built underground and you usually don't see them until they start eating up things in your house.)
Termites are "social" insects. The survival of the colony depends on the specialized services of three distinct castes, workers, soldiers and reproductives, which make up termite society. Two of these castes, workers and soldiers are readily observable the year round. The third caste, reproductives, live deep within the nest, and you usually only get to see them one time a year after the first big rain in the fall, when they develop wings and fly away from the nest in their attempt to establish new colonies.
To observe members of the soldier and worker castes, simply make a hole in a termite nest with a stick or other sharp object or brush away a small section of a termite trail. Soldier termites will rush out and crawl all over the disturbed area. The soldiers are light brown in color with dark mahogany-colored heads that end in a pointed proboscis. The workers quickly disappear back inside the nest or the trail, but will return a few minutes later to begin repairing the damage. The workers are lighter in color than the soldiers, have a larger abdomen, and their heads are more rounded, lacking the protruding proboscis.
The termite nest, or termitarium, is constructed by the worker termites out of chewed up and partially digested wood, which they cement together using their own saliva and feces. The termitarium consists of a complex maze of tunnels, passageways, and chambers. Nasutitermes nests can be quite large, reaching more than seven feet in length and four feet in width. An extensive tunnel system leads away from the nest, down the tree trunk, and along and under the ground. These tunnels, or galleries, can extend outward as much as a football field's length away from the home nest. The covered trails provide the blind and sun-sensitive workers access to food sources.
The worker termites are sterile females. Not only are they in charge of the building and repair of nests and trails, but they also locate, obtain, and provide food and water for all the other members of the termite colony.
Wood lice, as their name suggests, subsist on wood, usually obtained from broken branches and dead trees in the forest. They will also eat lumber, if it has not been treated with an anti-termite chemical, as well as other wood products such as paper or cardboard. Only rarely does this species eat the healthy wood of live trees.
Wood is not an easy food to digest, even for a termite. In order to accomplish this feat termites enlist the services of microorganisms that have the ability to break down the thick cellulose walls of wood cells and convert them into simpler and more digestible substances. In return, the microorganisms are provided with abundant raw materials in the form of chewed up wood as well as a nice safe place to live within the termite's intestinal tract. This mutually beneficial relationship is an example of the partnership that biologists call symbiosis.
Termites are not born with these microorganisms living inside them. They obtain them by a process called proctodeal feeding, whereby a young termite feeds on the liquid intestinal contents taken from the anal aperture of an older termite. The symbiotic microorganisms are contained in the intestinal material.
Once the chewed wood has had a chance to be broken down chemically with the aid of the microorganisms in the worker termite's intestines, the workers travel throughout the termitarium in order to feed the termite larvae, and the members of the other termite castes. The predigested food is then either regurgitated or excreted and presented to the patiently waiting recipients.
The soldier caste consists of sterile males dedicated to the security and defense of the colony. Their greatest military expertise comes in the form of chemical warfare. The soldiers have the ability to shoot out a sticky and strong-smelling chemical from the pointy proboscis located at the tip of their heads. This secretion can trap and poison small termite enemies, such as ants. Larger predators, such as birds and lizards are deterred by the irritating qualities of the chemical as well as by its disagreeable odor and taste. (If you have already experimented with disturbing tree lice nests or trails, you probably have experienced the turpentine-like odor of the soldier's chemical weaponry.)
The role of the termite king and queen, the most monogamous creatures on Earth.
In late summer the reproductive castes of St. John termites begin their preparation to leave their nest for the first and only time in their lives. They develop wings to fly with and compound eyes to give them the temporary sense of sight, which they will need in the vast and perilous world outside the confines of the termitarium. They also change from their usual pale color to a dark brown, the newly acquired pigment being necessary to protect them from the light of day. The transformed reproductives, now called alates, wait for the signal that will coordinate an airborne exodus of alates from all the different colonies in the area.
The awaited sign comes in the form of the first big rain in
autumn. When the rain stops and the sun sets, the alates fly
off en masse into the night sky. Termites are not strong flyers,
and their flight, although slow and drifting, is generally adequate
enough to put a modest amount of distance between them and their
home nest. The flying termites tend to be attracted by lights,
which is why you may come home some night after a big rain and
see hundreds of winged insects swarming around a lighted area
or crawling around your floor. Upon landing, their wings fall
off and it is possible that you will not see any bugs at all,
but will find piles of insect wings strewn about.
The airborne journey is just the beginning of the termite romance.
After the termites land and shed their wings, they pair off into
male and female couples. The female leads the way while her love
struck partner follows close behind. Together they search for
the location of their future home, which will most likely be
a crack or defect in a tree trunk or branch. The couple will
then work together to make a hole in the wood. When the excavation
is large enough, they will seal off the entrance with their feces.
The humble hollowed out section of tree now becomes a royal bedchamber
where the two previously undistinguished termites will live together
as king and queen "until death do they part".
Tropical termite queens can become quite large and may measure
as much as four inches long. The termite queen is well taken
care of by her comparatively tiny king, who spends most of his
life feeding and licking her. The queen can remain fertile for
as long as twenty-five years, and as she gets older and larger,
she may lay thousands of eggs per day.