Summary
This paper deals with the correlations of aggregation indices (K from negative binomial) of Acari and Collembola populations under Setaria sp.. in rotational and extensive pastures versus other factors, such as: air temperature, relative humidity, moisture and precipitation. The Arthropods were extracted from soil by modified Beriese — Tullgren funnels and the samples were collected from January to December, 1977. It was verified that aggregation indices show smaller aggregation in Acari than in Collembola. Correlation indices and studied physical factors do not explain completelly animal behaviour. It was observed that studied factors have major influence upon Acari populations than Collembola. and the variable of more influence is precipitation.