Bumblebees and Ants Battle in Violent Nectar Wars, Leading to Death and Food Shortage
The animal kingdom is known for bitter rivalries that sometimes break out into full-on feuds, like the conflict between bumblebees and Argentine ants. When these two insects meet, it’s not uncommon for them to duke it out over food from flowers. And the ensuing battle doesn’t end well for either one.
A new study published in the Journal of Insect Science documents a serious dilemma that bumblebees face when Argentine ants compete with them over nectar. Bees tend to avoid flowers already occupied by aggressive ants, which will bite to keep them away, but when they both get tangled in a fight, bees sometimes bite back. These skirmishes are a lose-lose scenario in most cases, leaving ants dead and bees with wasted energy that could’ve been spent feeding their colonies.
Read More: The Fragile Future of Solitary Bees
Argentine Protection Ants
Argentine ants are native to many South American countries, but have been introduced as an invasive species in several parts of the world, including European countries bordering the Mediterranean Sea, California’s coastline, South Africa, and Japan. Argentine ant colonies are known for their aggression, expanding rapidly into new areas and displacing native ant species.
In southern California, these ants can often be found in citrus orchards, where they’re quite the nuisance because of a special partnership with other pests. This takes the form of a quid-pro-quo deal with insects in the Hemiptera order (or “true bugs”), including psyllids, mealybugs, and aphids.
Argentine ants will protect these other insects from their natural enemies, and in exchange, they get easy access to honeydew — no, not the fruit, but a sugary liquid secreted by many hemipterans. The ants then harvest the honeydew gifted to them and return to their nests to feed the colony. They’ll also lead their hemipteran co-conspirators to new feeding sites, putting entire citrus orchards at risk of pest invasion.
Bumblebees’ Peskiest Nemesis
While Argentine ants are buddy-buddy with other pests, they’re not so fond of bumblebees. When ants that have settled on a flower are visited by a bee, they’ll bite it to keep it away from the nectar.
Naturally, these nectar thieves are bad news to bumblebees, which usually choose to avoid flowers with Argentine ants on them. However, they’re sometimes dragged into a fight when an ant starts biting.
Researchers involved with the new study wanted to see just what happens during this conflict. To do so, they observed over 4,300 individual behaviors from more than 415 bumblebees.
“With how important bumblebees are as pollinators, it made sense to try and understand more about what’s going on in these tiny nectar wars, because they could have a big impact,” said author Michelle Miner, a former University of California, Riverside entomology graduate student, in a statement.
The Toll of Nectar Wars
The researchers introduced six separate bumblebee colonies into a foraging arena with feeding sites that either had ants nearby or were ant-free. To no surprise, the bees were less likely to attempt feeding at a site with more ants.
Some bees did visit the sites with ants on occasion, though. When the ants started to bite, the bees responded not by stinging, but by biting back and decapitating them. This morbid outcome led to frequent bee victories in one-on-one fights, but this wasn’t necessarily a win for entire bee colonies.
Bees that fought with ants, the researchers found, were five times more likely to continue engaging in aggressive interactions rather than switch to nonaggressive interactions. These combative bees were also eight times more likely to continue aggressive interactions than to feed.
In other words, bees stuck in attack mode aren’t bringing back food to their colonies. How the colonies respond to the missing food isn’t yet known and is something that researchers hope to answer next.
Bumblebees that clash with ant antagonists may come away with injuries and no food, potentially leaving colonies hungry or down a member. Perhaps it would be best, then, for them to just be the bigger bee and move on to the next flower.
Read More: Ants May Amputate Other Ants to Save Them – Is This a Sign of Empathy?
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