Nest and soil populations of Trinervitermes spp. with particular reference to T. geminatus (Wasmann), (Isoptera), in Southern Guinea savanna near Mokwa, Nigeria.

Abstract

Nest and soil populations of Trinervitermes spp. were estimated on grazed secondary savanna woodland near Mokwa cattle ranch and on primary savanna woodland, 6 km from the ranch. Nest populations were estimated by obtaining a relationship between size of nest and the number of termites in the nest and using the relationship to estimate populations in measured nests within the study area.Mound populations of T. geminatus, by far the most abundant species, were 222 m-2 at a mound density of 232 ha-1 at the ranch, and 225 m-2 at a mound density of 175 ha-1 on primary savanna woodland. The mound population at the ranch represented a fresh weight biomass of 1.089 g m-2. Changes in abundance of the mound population of T. geminatus were correlated with breeding and foraging cycles. Maximum numbers (388 m-2, 2.03 g m-2) in August/September were reduced by the flight of alates and loss of foragers to predators; thereafter, the population continued to decrease (126 m-2, 0.57 g m-2) until the cessation of foraging in April/May and numbers of larvae and nymphs began to increase. Soil and mound sampling in primary and secondary savanna showed that although T. geminatus is a mound inhabiting species, two thirds of the mound plus soil population was outside the mounds giving a total population of 737 m-2 (3.08 g m-2). Alate production was estimated at 15.5 m-2 (0.19 g m-2) and neuter production at 367 m-2 (1.66 g m-2); production/biomass ratio was 1.0 T. togoensis (total population of 21 m-2) and T. occidentalis (200 m-2) had 90-96% of the total numbers outside the mounds, indicating that these two species were primarily subterranean.