A test of associative olfactory learning in the ant Formica clara (Hymenoptera: Formicidae); the power of a MaLER-based conditioning protocol

Abstract

In the present study, we tested associative olfactory learning performance of the ant Formica clara in laboratory conditions based on their MaLER responses. Ants were harnessed with the help of a paper-made holder and conditioned in two groups by forward pairing either limonene or eugenol (conditioned stimuli – CS) with a reward (unconditioned stimulus – US). After conditioning, memory tests were performed for each CS 15, 60 and 90 minutes following the conditioning in the absence of US. A further test was performed for each group with the CS of the other group to see if the ants showed an odor generalization. The frequencies of MaLER-positive responses during tests were used as indication of learning performance. Ants learned the association between the CS and US during conditioning for both odors and showed initially significant and gradually decreasing MaLER-positive responses during tests. The results showed that conditioning to the odors was absolute and no generalization was observed. We conclude that associative learning is a universal strategy for ants to adjust their behaviors to environmental changes around them and the MaLER technique is a powerful and easy to apply technique to test learning and memory capacities in ants.