Ecologia, comportamento e história natural da formiga ceifeira Pogonomyrmex naegelii (Formicidae, Myrmicinae) em Cerrado: ritmo biológico, dieta, área de vida, estrutura e demografia dos ninhos

Abstract

Pogonomyrmex naegelii belongs to the group known as harvester ants, which collects and stores seeds in underground chambers for later consumption. These ants can be found in both warm temperate and tropical regions around the world, especially in areas of semiarid to arid vegetation, although they may also be found in moist habitats. The following study provides a description of some aspects of the behavioral ecology and natural history of P. naegelii in cerrado vegetation (18º59 S e 48º18 W), in Uberlândia, MG, SE Brazil. Twelve colonies were observed weekly in the field, from May 2008 to June 2009, totaling 68 days and 177 h of observations (ad libitum/one observer). Three nests were excavated: two in 2008, being one in August and another in September, and one in June 2009. The species nests on the ground (~ 0.5 m deep) and colonies contain in average just over 400 workers. Nest entrances are inconspicuous (up to 1.5 cm in diameter) and are often covered with dry leaves, sticks or stones. Ant activity is diurnal (9 a.m. to 4 p.m. in the dry season; 11 a.m. to 6 p.m. in the wet season), positively correlated with air temperature and negatively correlated with relative humidity, with the activity peak, on both seasons, always in the period with the highest air temperature and lowest relative humidity of the day. Foragers leave the nest independently and individually search for food within the leaf litter or on bare ground, never searching on plants. The foraging areas varied in size from 3,32 to 29,22 m2 in the dry season and from 1,94 to 26,70 m2 in the wet season. Workers collect seeds (35 species altogether), flowers, fruits, vegetative plant parts, as well as scavenge dead animal matter. Seeds are more frequent in the diet during the dry season while animal itens are more frequent in the wet season. This is the first study on behavioral ecology of a Pogonomyrmex harvester ant in Brazil.