Brazilian ants diversity and the local geomagnetic field: a ferromagnetic resonance study.

Ants have the ability of homing and some species can migrate or move over long distances (nomadic). The presence of magnetic particles as geomagnetic sensors is the most accepted hypothesis to explain ant orientation mechanisms. The room temperature Ferromagnetic Resonance (FMR) spectra of migratory, nomadic, arboreal, trap-jaw and fire ants, applied to 11 samples are presented. The spectra were studied taking into account two components: the low field (LF) with a maximum at gmax values higher than 8 and the high field (HF) at the geff=2.1 with a linewidth of about 900 Oe. This study tests the systematization plausibility of ant magnetic material characteristics based on absorption spectra area and the ratios between the peak-to-peak amplitude spectral components (LF/HF). The HF component predominates in the spectra of the migratory and one nomadic ant, while the LF is the dominant one in the arboreal and six fire ants studied. The Solenopsis absorption spectra area, proportional to the magnetic material amount, increases as the local magnetic field intensity increases, suggesting an adaptation of these ants to the magnetic environment characteristic.