Treehopper Aggregation Tended by Ants - Publilia concava with Formica sp.

Treehoppers are often tended by ants as part of a mutualistic relationship. Treehoppers secrete honeydew, which is made mostly from excess plant sap that they consume. Ants "farm" the treehoppers for their honeydew. To do this, an ant grasps a treehopper and strokes it with its antennae. This causes a droplet of honeydew to appear at the tip of the treehopper’s abdomen, which the ant then consumes. Both insects benefit from this mutualistic relationship: The ants get honeydew, and in return, they protect the treehoppers from predators.

Female treehoppers deposit eggs along the midrib of host plants. Nymphs and adult treehoppers are tended by ants, and this tending has a strong positive influence on treehopper survival.

In this shot, there was one adult treehopper, numerous nymphs, hatched eggs, and ants (Formica sp.). They were on goldenrod (Solidago sp.) in a rural garden. The ants were dutifully tending the treehoppers :)