MI and PA Polistes fuscatus face learning

We test how plasticity contributes to geographic variation in individual face recognition in Polistes fuscatus wasps. Previous work has shown that Polistes fuscatus from Michigan, USA (MI) have variable facial patterns used for individual recognition, while Polistes fuscatus from central Pennsylvania, USA (PA) lack variable facial patterns and are unable to learn individual conspecifics. We experimentally altered rearing environment, so wasps were either reared with their own population or in a common garden with wasps from both populations. Then, we tested the wasps’ capacity to learn and remember individual conspecific faces.

Methods
Polistes fuscatus wasps were collected from the area surrounding Ann Arbor, Michigan (MI) (42°17′59″N, 83°39′46″W) and Rothrock State Forest, Pennsylvania (PA) (40°38′13″N, 78°4′29″W) in early-late June 2019 and 2020.

When a newly emerged worker was found on a nest, she was removed and painted with an individually identifying color code. Then, wasps were placed into a new enclosure of 4 newly emerged wasps with ad lib sugar and water. There were three treatment groups: 1) MI with MI, 2) PA with PA, and 3) PA and MI together (common garden, 2 PA and 2 MI). Wasps were housed with their treatment groups for 7 to 10 days. Then, wasps were trained to differentiate pairs of conspecific face images. Scores reflect learning accuracy (out of 10).