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Establishing their initial colony is probably the most critical moment in the life of leaf-cutting ants. The non-establishment is connected to abiotic and biotic factors, and the high mortality rates of initial colonies are possibly associated with entomopathogenic or antagonistic microorganisms to the symbiotic fungus present in the soil, hosted by these ants. Fire in the vegetation, depending on the intensity, is known to cause significant changes to the soil physical, chemical, and microbiological properties. The impact of a fire in savannah vegetation (Cerrado) on the establishment of early colonies of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) was evaluated. For this end, two areas were selected, one where there had been an accidental fire, and a contiguous one with the same size and vegetation characteristics without burning. In these areas and in soil collected in the same areas and stored in the laboratory, females recently fertilized in the nuptial flight were placed to excavate the soil and establish their colonies. Post-fire changes in the soil chemical and microbiological properties were quantified and correlated successfully in the establishment of new colonies of this leaf-cutting ant. Under field conditions, the females of A. sexdens rubropilosa did not show preference for which areas to excavate: the ones that had been burned or the ones that were unburned; under this condition, no colony survived according to the evaluation performed 120 d after the nuptial flight. Under laboratory conditions, the majority of the females excavated the soil, whether it had been burned or not. However, the establishment of initial colonies was significantly higher in soils collected far from the surface and in areas that had not directly been affected by the fire, showing a negative effect of fire on colony establishment under laboratory conditions. [ABSTRACT FROM AUTHOR]

The nuptial flight allows males and females to meet and copulate and both need energy to perform this activity. Before leaving the nest, males and females are well nourished and ready to mate. However, little is known about the lipid and energy contents in females before the nuptial flight (virgins) and after it (mated females). In this work we measured lipid concentrations in relation to body weight in these individuals. Our results showed that 16.82% of the bodies of young virgin females one month before mating flight are composed of lipids, contrasting with the 32.62% lipid content in mated females who had not excavated their nest yet, and 32.88% in those who had. The energy content measured for virgin females was 2942.63 J, contrasting with 6110.01 J for queens before excavating the nest and 5677.51 J after excavation. Based on our results, we conclude that the body mass, and therefore the lipid and energy contents in the bodies of Atta sexdens rubropilosa queens double during the last month before the nuptial flight. This energy resource is fundamental to the activities required during the nuptial flight, digging the nest and the founding of the colony.O vôo nupcial permite que machos e fêmeas se encontrem e copulem. Para isso, tanto o macho quanto a fêmea precisam de energia para efetuar tal atividade. Antes de partir do ninho de origem, machos e fêmeas estão bem nutridos e prontos para o acasalamento. Mas pouco se conhece sobre o teor de lipídeos e conteúdo energético pré-vôo nupcial (fêmeas virgens) e pós-vôo nupcial (fêmeas acasaladas). Nossos resultados indicam que as fêmeas virgens apresentaram 16,82% de lipídeos em seu corpo, enquanto as rainhas (fêmeas acasaladas) que não escavaram 32,62%, e as que escavaram 32,88%. O conteúdo energético foi de 2942,63 J para as fêmeas virgens, 6110,01 J para rainhas sem escavação e 5677,51 J para aquelas que escavaram. Com base nos resultados obtidos, concluí-se que as rainhas de Atta sexdens rubropilosa dobram a sua massa corporal, e consequentemente, o teor de lipídeos e conteúdo energético, um mês antes da revoada. Esse recurso energético é fundamental para as atividades exigidas durante o vôo nupcial, escavação do ninho e a fundação da colônia.