First-year nest growth in the leaf-cutting ants Atta bisphaerica and Atta sexdens rubropilosa

Abstract

The majority of ants construct nests underground to maintain environmental conditions favorable to the development of immature and adult individuals. But little is known about nest growth. Thus, we studied the growth of nests of the leaf-cutting ants Atta bisphaerica Forel 1908 and Atta sexdens rubropilosa Forel 1908 from foundation until the appearance of a second chamber. To this end, we verified the measurements of the chamber recently constructed by the queen and monitored the dimensions of its enlargement in the initial phase of nest development. The nests were marked in nuptial flight, in 2007, with 40 nests of each species being dug at 45, 90, 135, 180 and 225 days afterward. As a result, a semi-spherical format was verified in both species in the initial chamber, and throughout the process of enlargement the chamber came to present a spherical aspect. The chamber size increased along with nest age, especially its height and, consequently, depth. In A. bisphaerica the height rose 2.7 cm and the depth increased 4.4 cm, from foundation to the age of 225 days. For A. sexdens rubropilosa the respective height and depth increases were 1.3 cm and 3.8 cm, up to 225 days. In both species, construction of the second chamber began 135 days after nest foundation. These results are new and add to information on the growth of leaf-cutting ant nests.

Keywords

• excavation
• initial chamber
• leaf-cutting ant
• nest architecture
• nest foundation