Leafcutter Ants in Southern Amazon Forests, Brazil

This study aims to identify the species of leafcutter ants, the infestation rate and the spatial distribution of anthills in forest plantations in Alta Floresta-MT. The samples were collected in five plots, with I and II being a Eucalyptus urophylla × Eucalyptus grandis hybrid plantation, III a consortium of Brazil nuts (Bertholletia excelsa) and rubber tree (Hevea brasiliensis), IV and V plots of Tectona grandis. The size of the anthills were measured, obtaining the area in square meters of loose ground, were classified into size classes I- ≤ 1 m2; class II- 1.1 to 2.9 m2; class III- 3 to 8.9 m2; class IV- 9 to 25 m2 e class V- > 25 m2. To calculate dispersion, the Dispersion (DI) and Morisita Index (IϬ) were used. Only one species was observed in all plots (Atta sexdens rubropilosa Forel, 1908). 838 nests were mapped in the five sampled plots, the total average density of anthills found in the plots was 26 anthills/ha. The average total area of loose soil occupied by anthills was 590.05 m2, the distribution of anthills between size classes showed 86.87% disproportion with the anthills in class I. The distribution of the anthills in the five plots that were evaluated were of the aggregate type, following the Morisita Index and the Dispersion index.