Mounds of Cathedral termites dominate the landscape in the arid Northwest Territory.
Bug of the Week’s last stop in Australia is the Northwest Territory, home of one of the most remarkable bunch of engineers in the insect world, the Cathedral termites. Mounds of the Cathedral termites on the dry plains of the Northwest Territory dominate the landscape and often tower more than 15 feet in height. Constructed from mud, plant parts, and termite saliva and feces, the columns of the mound are extraordinarily tough and able to withstand the rigors of wind, rain, heat, and hungry predators. Construction of the hollow columns allows for internal circulation of air from the cooler soil at the base of the mound to the warmer top. This clever ventilation provides a central air-conditioning system that enables the colony to remain relatively cool even when the external temperatures are bloody hot.
Light colored mud tubes in the grass mark the foraging routes of termites as they search for food.
As a group, termites consume both living and dead plant material. To utilize the nutrients tied up in plants, termites rely on symbiotic bacteria and, in some primitive species, protozoa, which inhabit their gut to help digest the rugged plant material called cellulose. Termites have an unusual and rather crude way of passing these vital microbes from one termite to the next. Through a process known as proctodeal trophallaxis, one termite excretes a droplet of microbe-packed fluid from its anus and this packet of goodies is consumed by another termite waiting at the rear end. Yum! The transfer of liquids from one termite to the next 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 other insects such as the green tree ants we visited last week. Social insects such as termites and ants have a distinct division of labor with a caste system that includes specialized workers, soldiers, and reproductives.
A breech in the wall of the mound brings squads of nasute soldiers to the defense of the colony.
Termite reproductives are called kings and queens. Queens produce thousands of eggs that hatch and develop into workers, soldiers, and new reproductives. Workers perform a variety of tasks including tending the young, feeding the queen and soldiers, and gathering food. Termites are not creatures of the light. They live in subterranean nests, inside trees and fallen logs, or within the dark chambers of their mighty cathedrals. Radiating from these nests were tunnels of soil, wood, and excrement that enabled the termites to move across the arid plane to nearby trees, shrubs, and grasses to gather vegetation and bring it back to the nest to feed the brood and queen. One of the students tested the resolve of a termite colony by breaching the column with his hand. Soldiers from deep within rushed to the hole to defend the colony.
The termite soldier squirts defensive chemicals at enemies through the elongated snout on its head.
In some species of termites, soldiers are armed with jaws that stab, cut, or snap at and whack an enemy. The termite soldiers in the cathedral mounds were chemical warriors known as nasutes. These highly evolved termites have dark brown heads with a long, tubular snout. From this snout, called a nasus, they squirt sticky defensive secretions that can entangle, irritate, and repel invading enemies such as ants. A hand or finger placed over the breach in the nest was soon coated with sticky liquid provided by the nozzle-headed soldiers. Some of the more adventurous humans sampled the termites to learn why so many other insects, birds, and Aborigines seek a termite buffet. While I found the delicate flavor reminiscent of carrots Julienne, some of the students said the termites tasted, well, like bugs.
References
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 the students and faculty of BSCI 279A, Natural History, Ecology, and Geology of Australia, for providing the inspiration for this story. For more information on Cathedral termites, please visit the following web site:
http://www.itsnature.org/ground/creepy-crawlies-land/termites/