A Survey of the Arthropod Soil and Litter Fauna of Some Forest Reserves and Cacao Estates in Trinidad, British West Indies

Abstract

In addition to samples of the surface litter, soil samples were taken with a core auger 3.6 in. in diam. to a depth of 9 inches. A flotation process extracted the fauna from the soil which involved mixing the soil with a salt soln., bubbling air through the mixture to disentangle the animals, straining through muslin, boiling in tap water to kill the animals, adding kerosene to take up all chitinous animals, and finally decanting through muslin. Three undisturbed rain forest reserves and 4 cacao estates were sampled during the rainy season of 1943. Certain groups (Hoploder-matid mites, termites, Nematocerous fly larvae) occurred in large numbers only in specialized soil habitats. The general soil fauna was considerably more abundant in the reserves than in the estates. The prevalent plant community had a greater influence on the size of the soil population than the soil-type, although the latter influenced the type of arthropod present. In all localities, the Acarina were the predominant animals in the soil and litter. Although their populations in ecologically different areas were sometimes numerically the same, qualitative constitution of the populations might differ. Abundance decreases after the first 2-3 in. depth, many forms do not migrate deeper than 6 in., and only mites and ants occur in numbers at 9 in. In light sand, penetration is deeper. A surprisingly large population of Ortheziine scale insects attacking young cacao rootlets was probably doing economic damage on one estate.