Castes in humivorous and litter-dwelling neotropical nasute termites (Isoptera, Termitidae)

The developmental pathways of the neuter castes were studied in three species of Nasutitermitinae from central Panama. The humivorous Subulitermes denisae and Coatitermes clevelandi display several primitive traits: absence of sex dimorphism, representation of both sexes among workers and soldiers, and occurrence of successive worker instars. The litter-dwelling Velocitermes barrocoloradensis has a more complex caste system: female larvae are larger than males and give rise to the large workers, which constitute the bulk of the work force; male larvae proceed to soldiers through a small worker or a special larval instar. The resulting soldier caste is polymorphic. These results support previously formulated hypotheses regarding a link between humivorous diet and reduced polymorphism on the one hand, and between forest-floor foraging and large continuous size variation among soldiers on the other. Whereas the caste systems of Subulitermes and Coatitermes probably represent a primitive condition, Velocitermes shares derived traits with Nasutitermes and the other fully nasute genera previously studied. I therefore hypothesize that ancestors with these advanced features may have spread from the neotropics and be at the origin of most nasute genera, including humivorous taxa, present in other regions.