Timing is everything for the mutualistic relationship between ants and acacias

In the 1960s, Penn biologist Dan Janzen, as part of earning his Ph.D., re-described what has become a classic example of biological mutualism: the obligate relationship between acacia-ants and ant-acacia trees. The acacia trees produce specialized structures to shelter and feed the ant colony, and the ants, in turn, defend the tree against herbivores.

source https://www.lifetechnology.com/blogs/life-technology-news-blog/timing-is-everything-for-the-mutualistic-relationship-between-ants-and-acacias