Quantitative variations of Constrictotermes cyphergaster (Isoptera) instars over time in a Neotropical semiarid ecosystem

Abstract

The presence and relative proportion of termite castes can vary according to both intrinsic characteristics of the colony and in response to external stimuli. Constrictotermes cyphergaster is a Neotropical termite that demonstrates high densities of arboreal nests in open vegetation ecosystems in Brazil. Numerical variations of the instars in 30 nests of this specie were analyzed over 1 year in the semiarid Caatinga vegetation of northeastern Brazil. The number of individuals per instar was estimated from five subsamples (5 ml) taken from each colony. The abundance of most instars varied significantly among the nests sampled within the same month. Between months, there was significant numerical variation in the numbers of second instar larvae, workers, presoldiers, soldiers and fifth instar nymphs. In the nymphal line, only the fourth instar was found in all months, whereas alates were only found in February, the month with the highest recorded rainfall. With increasing proximity of the swarming event, there was an increase in the differentiation of last two nymphal instars, with subsequent investment in the differentiation of apterous instars and the emergence of early nymphal instars. These results indicate that differentiation of the instars of C. cyphergaster is synchronized with the regional climatic cycle and the annual production of alates. However, there was substantial numerical variation between the instars of the colonies sampled at the same time points, suggesting that factors intrinsic to the colony can generate heterogeneous feedback along with responses to environmental factors.