The purpose of this study was to track year-to-year variation in arthropod communities of the host plant Ligusticum porteri (Apiaceae). We used pitfall traps to sample the ants at each of twenty sites containing populations of L. porteri. Sampling took place once at the end of June in each study year. We randomly placed pitfall traps made from 50 mL centrifuge tubes at three locations per site. The pitfall traps remained in the soil for 72 hours. We identified ants to species using a location-specific taxonomic key.