Use of olfactory and visual cues for orientation by the ant Myrmica ruginodis (Hymenoptera: Formicidae)

Cammaerts, M.-C.; Rachidi, Z.; Beke, S.; Essaadi, Y.

Abstract: Myrmica ruginodis Nylander, 1846 foragers were differentially conditioned to two olfactory and two visual cues. The ants were then placed in mazes provided with either olfactory cues, or visual cues, or with successively or alternatively set visual and olfactory cues. In the latter case, the ants scored consistently higher in front of visual cues. The conditioned ants perfectly negotiated mazes provided with correct visual cues and wrong olfactory ones, but moved incorrectly through mazes provided with wrong visual cues and correct olfactory ones. M. ruginodis foragers thus primarily used visual cues to orient themselves when traveling, neglected olfactory cues and continued to respond to visual cues even if they became obsolete. However, when responding to olfactory cues, the ants responded to the actual odor and not to the visual perception of the odorous object, and were able to discriminate amongst the odors. M. ruginodis workers also distinguished differently colored cues. Unexpectedly, they failed to respond to the lower vertical part of the learned visual cues and responded entirely to the upper part of these cues. This means that when foraging or traveling, their main field of visual perception is above them and not in front of them. Under conditions of low light intensity (< 5 lux), M. ruginodis workers could no longer respond to visual cues. In such instances, they relied on odorous elements to find their way and did so better than under high light intensity. They responded to olfactory cues under low light intensity, even if wrong visual cues were added and even if the olfactory cues were incorrectly set in the mazes. In the latter case, the ants progressively stopped responding to the obsolete olfactory cues. The navigation system of M. ruginodis differs from that of M. sabuleti Meinert, 1861 and is in agreement with the typical environment of the species and the morphology of the eyes.

Myrmecol. News 16: 45-55; printable