by Sara LaJeunesse, Pennsylvania State UniversityWhen eight-year-old Hugo Deans discovered a handful of BB-sized objects lying near an ant nest beneath a log in his backyard, he thought they were a type of seed. His father, Andrew Deans, professor of entomology at Penn State, however, knew immediately what they were—oak galls, or plant growths triggered by insects. What he didn't realize right away was that the galls were part of an elaborate relationship among ants, wasps and oak trees, the discovery of which would turn a century of knowledge about plant-insect interactions on its head.
Looking back, Hugo, now 10, says that he "thought they were seeds, and I felt excited because I didn't know ants collected seeds. I always thought ants would eat food scraps and stuff around the house. Then I got more excited when [my dad] told me they were galls, because [my dad] was so excited. I was surprised that ants would collect galls because why would they do that?".
According to Andrew Deans, who is also the director of Penn State's Frost Entomological Museum, many plant-insect interactions are well documented. For example, most "cynipid" wasp species have long been known to induce oak trees to produce protective galls—or growths—around their larvae to ensure the safety of their developing offspring.
Additionally, certain plants—including bloodroot (Sanguinaria canadensis), a wildflower native to North America—produce edible appendages, called elaiosomes, on their seeds to attract ants, which then disperse the seeds by carrying them back to their nests. This latter example is referred to as "myrmecochory"—or seed dispersal by ants."In myrmecochory, ants get a little bit of nutrition when they eat the elaiosomes, and the plants get their seeds dispersed to an enemy-free space," Deans explains. "The phenomenon was first documented over 100 years ago and is commonly taught to biology students as an example of a plant-insect interaction."