Fig. 2.

Modulation of behavior displayed by low-level–infected ants toward contaminated nestmates. (A) Aggression, (B) allogrooming, and (C) poison spraying were performed equally toward nestmates contaminated with Metarhizium (black) or Beauveria (gray) but depended on the ants’ infection state, which was either no prior infection or a low-level infection of a pathogen homologous or heterologous to the pathogen the nestmate was contaminated with. (A) The aggression level of low-level–infected ants was higher compared with noninfected controls but did not differ when the nestmate was contaminated with the homologous or heterologous pathogen. (B) Grooming was performed significantly longer by low-level–infected ants to a nestmate contaminated with the homologous pathogen, compared with both noninfected control ants and low-level–infected ants grooming nestmates contaminated with heterologous pathogen. (C) Poison spraying was essentially absent in noninfected control ants but increased in low-level–infected ants interacting with a nestmate contaminated with the homologous pathogen and was increased further when the nestmate was contaminated with the heterologous pathogen. Mean ± SEM displayed separately for Metarhizium and Beauveria, with the line indicating a nonsignificant difference between the two pathogens; different letters indicate groups that differ significantly in post hoc comparisons using Benjamini–Hochberg correction for multiple testing at α = 0.05. Sample size n = 720 ants in 144 independent replicates. For the number of ants engaging in the particular behaviors see Fig. S3. Supporting data are given in Dataset S3. For the behavior toward noncontaminated control nestmates see Fig. S4 and Dataset S4.