Natural enemy of Argentine ants discovered by Stanford students
Clark Pest Control
When customers call Clark Pest Control about an ant infestation, more often than not the culprit is the Argentine ant (Linepithema humile), an invasive species that takes over wherever it’s introduced. Most ant species carry a “recognition” chemical on their exoskeletons that worker ants use to identify other members of their colony, and will go to war with members of competing colonies, even those of the same species. Argentine ant colonies, however, will cooperate with one another, organizing in supercolonies with many queens. In California, one such supercolony is estimated to stretch from San Diego in the south to Ukiah, 115 miles north of San Francisco.
Argentine ants, when they take over a piece of ground, will overwhelm and eliminate any competing ant species active there, which is something they’ve done in temperate zones around the world. The problem created is that many of the vanquished ant species have evolved to develop a symbiotic relationship with a specific plant species in their environment – think of how plants need bees to pollinate their flowers. When Argentine ants prevail, those plants are left without assistance from their insect handmaidens.
As Louis Bergeron originally reported, which was posted on Stanford University’s online news site, undergraduate students at a Stanford summer course discovered one ant species that wasn’t letting an Argentine ant incursion gain the upper tarsus. The students observed winter ants (Prenolepis imparis) taking care of their ant business in the field one day, and the next day they found a battleground strewn with dead Argentine ants. Intrigued, they isolated groups of both species in a Petri dish, and saw that, when overwhelmed by Argentine ants, the winter ants would excrete a drop of poison from the tips of their abdomens and then dab the Argentine ants with it, which would neutralize them – with a 79-percent kill rate.
Both Argentine ants and winter ants will tend, or “ranch,” aphids, because aphids secrete honeydew, an intensely sugary fluid the ants crave as food. But winter ants don’t form supercolonies, and they don’t thrive in the warm Mediterranean climate found in large parts of California, so there’s no chance they might develop into a natural answer for the Argentine ant problem. However, once the chemical agent used by the winter ants to kill the Argentine ants is isolated by scientists, perhaps nature will have provided an answer to one of the more vexing invading-species problems in the global environment. – Jackson Griffith
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