Termites are insects from the order Isoptera. These insects are important economically, since they cause damage to wooden structures. Although not closely related to bees, wasps and ants, members of the order Hymenoptera, these social insects display a similar pattern or social behavior. Some believe that these insects are most closely related to cockroaches, and, to quote a rhyme,
"A primitive cockroach knocked on wood
tasted it and found it good
and that is why your aunt May
fell through the parlor floor today."
Termite colonies in the soil or wood are composed of several different castes. Workers generally excavate new tunnels and chambers and do other housekeeping tasks in the colonies. Soldiers use fearsome jaws, or, in some species, use tubes on the heads to shoot fluids at intruders. Some species of termites have members that are specialized to plug entrances with their huge cork-like heads. The reproductive castes produce the offspring to expand the hive. In some cases, the worker castes are not adults, but juveniles, and some of them are capable of developing into reproductive individuals.
Termites are only able to digest the cellulose in wood because of protozoans present in the gastric caecum, a pit in the digestive tract of the insects. These protozoans are not transmitted at birth; termites often eat the feces of other termites to obtain them, or place their mouthparts onto the terminal end of the abdomen of other termites to introduce them to their digestive tract.
Within the order of Isoptera, there are two economically important families, the Kalotermatidae and the Rhinotermatidae, which are of most concern to us. Kalotermatidae are the drywood, dampwood and powderpost termites, and these build their colonies exclusively in the wood. Rhinotermatidae, on the other hand, are the subterranean termites which build their nest partly in wood and partly in the soil. This is an important distinction, because fumigating the infested wood works well for Kalotermatidae, but doesn't work as well for Rhinotermatidae. There other families of termites, which include the impressive mound building termites which create elaborate solid structures which dot the landscapes of arid regions. It is said that a bit of the "soil" used to make these mounds is an effective repellant for other insects.