Influence de la sécheresse sur le peuplement en termites

Abstract

The almost total lack of rain in Northern Sénégal during 1972 had a manifold effect upon the populations of termites living in the IBP quadrat at Fété Olé. Some species were found living at a greater depth than usual and nests tended to cluster around tree stumps, other nests or in more humid areas. Fungus gardens of Macrotermitinae were also built deeper within the soil, while those of Bellicositermes bellicosus were frequented by larvae only in the central core of the nests. Building behavior was diminished or absent. A change in diet was noticed in foraging species of genus Trinervitermes which turned upon dead wood to serve as a substitute to dry grass. Swarming was delayed or did not take place at all ; winged individuals could thus be found in some Trinervitermes nests five months after their usual swarming period. Galleries of Microter-mitinae have been found at a depth of 50 meters, close to the water table. Generally speaking, an almost rainless year increases the mortality rate of already established colonies among species building their nests above ground. Paradoxically, the number of new colonies of Bellicositermes bellicosus was increased after the 1972 drought ; a possible explanation of this effect is discussed. The species whose colonies entirely lived underground were little affected by the lack of rains. During the rainless period, the consumption of dry grass by termites decreased significantly, whereas that of dead wood showed a definite increase.