Ness J. H., Morris W. F., Bronstein J. L., Integrating quality and quantity of mutualistic service to contrast ant species protecting Ferocactus wislizeni, Ecology, 2006, 87(4):912-921, doi: 10.1890/0012-9658(2006)87[912:IQAQOM]2.0.CO;2
The abstract presents a comparison of four ants that protect Ferocactus wislizeni. An experiment with added Manduca sexta caterpillars assesses attacks on potential herbivores. Visit frequency, worker number and the effectiveness of individual workers contribute to protection associated with fruit maturation. The abstract was used, without detailed parameters from the full protocol.