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Parasitic Ant Queens Spray Chemical That Turns Workers Against Their Own Queen

The study in Current Biology reports that queens of Lasius orientalis and Lasius umbratus infiltrate related nests and spray an abdominal secretion (likely formic acid) onto the resident queen, changing her scent so workers perceive her as an intruder. Workers then attack and kill their own queen, after which the parasitic queen returns to lay eggs and take control. The tactic is rare, highly efficient for the intruder, and appears to have evolved independently in both species.

08:17 AM, 11/28/2025Science
Parasitic Ant Queens Spray Chemical That Turns Workers Against Their Own Queen

Researchers have documented a striking form of social parasitism in ants: invading queens from certain Lasius species chemically alter the scent of a colony's resident queen so that workers attack and kill her, allowing the intruder to take over the nest.

The study, published in Current Biology, focuses on newly mated queens of Lasius orientalis and Lasius umbratus, known as temporary social parasites. Instead of founding a new colony, these queens sneak into nests of closely related species (for example, Lasius flavus and Lasius japonicus) and adopt the colony odor before striking.

According to the authors, the invader first blends in by acquiring the colony's chemical profile. Once camouflaged, she approaches the resident queen and fires multiple jets of a sharp-smelling abdominal secretion—most likely formic acid—onto her. That spray appears to mask or change the host queen's scent cues, making her smell like an intruder to the workers.

Keizo Takasuka, a behavioral ecologist at Kyushu University, said he was 'lost for words' when he saw workers suddenly turn on their own queen after her scent was altered.

With the colony's recognition system disrupted, workers attacked and killed their mother in an episode of matricide that provides no obvious benefit to the doomed queen or her offspring. The parasitic female then retreats briefly, returns once the resident queen is gone, begins laying eggs and assumes control of the workforce.

Entomologists describe the tactic as both efficient and brutal. Direct attacks on a host queen are risky because workers typically defend her; by chemically manipulating recognition cues, the invader co-opts workers to do the killing. Evolutionary biologist Christian Rabeling called the process "very brutal."

The researchers also found evidence that the two parasitic species evolved this chemical-manipulation strategy independently, suggesting the tactic may have arisen multiple times. The study authors note that ant groups lacking formic acid might achieve similar effects with other chemicals, though such alternatives have not yet been confirmed.

Overall, the findings expand our understanding of how sophisticated and weaponized chemical communication can be in insect societies, and they highlight a rare example of matricide driven entirely by an infiltrating parasite.

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