Plants are far from helpless in their efforts to repel herbivores. They can cover themselves with thorns, make themselves taste bad, or produce leaves that are difficult to digest, just to name a few examples. However, my personal favorite strategy is the purchasing of protection that occurs when plants produce extra-floral nectar to attract ants. Ants are major and effective predators, but are also attracted to sweets. Plants can induce ants to swarm about on their leaves and stems by producing droplets of a sweet liquid.
I notice this phenomenon most frequently on sunflowers, especially plains sunflower (Helianthus petiolaris), an annual plant common on sandy soils around Nebraska. Over the years, I’ve photographed a number of ants that have been drawn to sunflowers by the extra-floral nectar those plants have produced. Below is a selection of those images. The ants aren’t a foolproof strategy, and sunflowers still get eaten by lots of animals – large and small. Regardless, it’s an admirable and fascinating tactic in sunflowers’ fight to survive and reproduce.