Insect cuticles are protected from drying out and abrasion by a thin layer of waxes and cuticular hydrocarbons (CHCs). These epicuticular waxes are produced by secretory cells which lie beneath the epidermis (see below)
The importance of this epicuticular layer in preventing the insect from drying out has been known for a long time, but more recently, there has been an explosion of studies investigating the role of the cuticular waxes in terms of communication.
Insects can tell a lot about each other simply by touching with their antennae!
Without going into too much detail, the diversity of cuticular hydrocarbon compounds in the outer layer of the insect provide it with a sort of chemical language. The different chain lengths of the hydrocarbons, their degree of saturation (the number of double bonds), and the number and positions of methyl groups provide a sort of Rosetta stone which can communicate all sorts of things about the insect.
Simply by touching the cuticle of another insect with their sensitive antennae – covered in different types of sensors – an insect can ‘read’ all sorts of things about the other insect, written in wax, as it were!
The chemical language of cuticular hydrocarbons enables insects to communicate information about their identity (genus, species) their gender (is this a male or a female I am touching?), caste, age, physiological state and even mating status (have you mated before you met me?!).
The chemistry of CHCs provides a near endless series of possible combinations, with over a hundred different epicuticular components present in some insects.
Cuticular hydrocarbons are particularly important among social insects, like ants, bees and termites, because of the need to identify nest-mates, including different castes (workers, foragers, queens and so on), and invaders (parasites).
Ants analyse the hydrocarbons on the cuticle of another individual to determine if it is an intruder.
Cuticular hydrocarbons are also used as contact sex pheromones in several beetle families.
These chemicals on the surface of an insect convey a lot of information about its identity, sex and health for example, but they will also be ‘read’ – tasted – by another insect in combination with other signals, what it can see and smell for example.
Chung, H., & Carroll, S. B. (2015). Wax, sex and the origin of species: dual roles of insect cuticular hydrocarbons in adaptation and mating. BioEssays, 37(7), 822-830.
Holze, H., Schrader, L., & Buellesbach, J. (2021). Advances in deciphering the genetic basis of insect cuticular hydrocarbon biosynthesis and variation. Heredity, 126(2), 219-234.
Mitov, M., Soldan, V., & Balor, S. (2018). Observation of an anisotropic texture inside the wax layer of insect cuticle. Arthropod structure & development, 47(6), 622-626.