Chemical Defense and Self-Defense in Termites

Summary

Termite soldiers are unique among insects in the variety of chemical weapons and morphological adaptations they use for colony defense. The three main types of chemical defenses are: (1) biting, with the injection of an oily or toxic material into the wound; (2) brushing, with the topical application of an irritant or contact poison onto the cuticle of an attacker; and (3) glue-squirting, in which a viscous, terpenoid secretion is ejected at an aggressor.

The oily secretions of the first group have been identified as normal alkanes and alkenes unusual new irregular diterpenes, and very large-ring (up to C₃₈) macrocyclic lactones. The contact poisons of the second group are electrophilic lipids, such as nitroalkenes, vinyl ketones, and 3-ketoaldehydes. A substrate-specific reductase allows autodetoxication of these poisons by conspecific workers. The third group, the glue-squirting nasutes, produces an array of bi-, tri- and tetracyclic diterpenes based on intramolecular cyclizations of cembrene-A. The identification of these chemicals and their importance in termite biology and evolution will be discussed.