Termites and Termites Aphids – The Soldier Caste
WouterTermites have developed numerous ways to defend themselves against predators. Some species produce toxic chemical while others actively squeeze their abdominal muscles until they explode. Several species defecate on their enemies. Some termite species live in dead trees while others nest in shrubs. The specialized soldier caste is one of the main defensive forces.
Workers of Nasutitermes costalis secrete terpenoid secretions in order to control the growth of the microbe that is found in the nest. They also act as foraging scouts.
These specialised altruistic behaviours are beneficial for the colony as a whole. However, their evolution may have been driven by competition with other colonies. This is likely because some of these species nest separately. This may lead to an evolutionary trade-off between the soldier and worker-first lineages.
In social aphids, the evolution of the soldier caste has been driven by predation risk. These parasites exploit social interactions and redirect altruistic behaviours. In snapping shrimps, soldier development is likely driven by intraspecific competition.
The sterile worker caste of social insects has evolved specialised altruistic behaviours. These behaviours include self-destructive behavior, such as suicide rupturing. This defence mechanism is called autothysis. In a few species, this defensive behaviour has evolved independently.
The specialised soldier caste is also responsible for colony reproduction. In some species, workers can step in to replace king and queen if they die. They are also responsible for transporting eggs when a colony is disturbed.
The evolution of the soldier caste in termite and social aphid species is influenced by predation risk and food resources. When food is abundant, a greater proportion of soldiers are produced. Similarly, if food resources are scarce, a lower proportion of soldiers are produced. Alternatively, high competition may lead to the evolution of the soldier caste.
