Termites at Work & at War

Defense mechanisms for most termite colonies depend on castes

By DR. STUART MITCHELL

An exceedingly organized and integrated society, the termite colony (termitarium) utilizes a caste system. A termitarium divides its labor system by the structure, function, and behavior of colonial members. Reproductives, workers, and soldiers are the primary castes. Reproductives are referred to as primary and secondary (or supplementary). Workers and soldiers are perpetually at work and at war!

As the prevalent number of individuals within the colony, workers are generally whitish in color, soft-bodied, and possess hardened mandibles and mouthparts highly functional for chewing. Workers are laborious, forage and gather food, feed and groom colonial members, and both construct and maintain the nest. Directly responsible for the potentially significant destruction termites can cause is the cryptic worker caste. A true worker caste is absent within some primitive termite families. Pseudo-workers or pseudergates (which may molt without changes in size) are immature individuals that carry out tasks in primitive termite families.

Most termite species have both worker and soldier castes. Wingless and generally lacking eyes, workers and soldiers are the sterile castes. Lacking fully developed reproductive organs; workers and soldiers can be either male or female. Dimorphic (two sizes) in some species, the larger individuals are named major workers or soldiers and the smaller minor workers or soldiers. Trimorphic soldiers exist in a few termite species.

For the soldier caste the main function is defense. Blind, most termite soldiers locate enemies through both tactile and chemical cues. Typically, the termite soldier has a pronounced, dark, and hard head with powerful mandibles which may be hooked and contain teeth. Soldiers’ head and mandibles allow for defense of the colony against predators, such as ants.

When attacking, soldiers perform rapid lunging movements while opening and closing mandibles in a scissor-like action. Any predator foe may be lacerated, beheaded, and/or dismembered. In Capritermes, the soldiers’ mandibles are asymmetrical and snapping. The right mandible blade-like and the left mandible twisted and arched. Producing a loud click during defensive events, the mandibles lock together and release (like fingers snapping). Cryptotermes soldiers use their short and truncated heads (phragmotic) to obstruct the termitarium entrance holes.

With chemical mechanisms of sticky, toxic liquids secreted by either the salivary or frontal glands, Termitidae (higher forms of termites) may enhance or replace mandibular defenses. Entangling enemies, whitish or brownish liquids become rubberlike after exposure to air. In Coptotermes and Rhinotermes the frontal gland occupies a vast portion of the abdominal cavity; opening by means of a frontal pore (fontanelle) via which liquid is secreted. In Rhinotermes the minor soldier secretes a liquid from the frontal pore that flows down a groove within the elongated labrum to a hairy tip. There it volatilizes into a repellent gas.

In Nasutitermitinae, soldiers’ mandibles are reduced in size and non-functional with reliance upon chemical defenses. With an elongated head shaping into a long snout (nasus), the frontal gland, which occupies a major portion of the head, opens at the end of the snout. Over several centimeters, and with good accuracy, Nasute soldiers can eject a clear, sticky, resinous liquid at predators. In a few termite Genera a soldier caste is lacking and the mechanisms for defense in these groups are not well understood.

Whether termite workers at work or termite soldiers at war, pest management professionals are vigilantly on the front lines battling termite infestations to protect structures and properties.