Queen of Parasitic Ants Lasius eastern (left) penetrates the nest Lasius yellow and approaches his queen (right)
Keizo Takasuka/Kyushu University
One species of parasitic ant takes over colonies of a related species, inciting workers to kill their queen and then taking her place.
About 230 species of ants are considered parasites: they lay eggs in colonies of other species or steal their larvae and pupae. Some kill host queens before laying their own eggs and convincing workers to serve them instead.
Keizo Takasuka from Kyushu University in Fukuoka, Japan, and colleagues observed that when the queen of a parasitic species Lasius eastern was accidentally brought into the nest of his relative, Lasius yellow, yellow then the workers will kill their own queen – their mother.
Many parasitic queens are killed by workers as soon as they are discovered, but some overcome the colony's defenses by apparently enveloping themselves in the colony's scent.
To track how the parasitic queens became successful, the researchers helped them by covering the intruder females with the scent of worker ants before introducing them into the colony.
“It's reminiscent of a zombie TV show. The Walking Deadwhere characters smear themselves with walker blood to get through a crowd—it involves a disguise that often fails, and those exposed are brutally killed,” says Takasuka.
Once the parasite enters the colony, it sprays the rival queen with a chemical, presumably formic acid, through an opening at the tip of its abdomen.
The workers interpret this chemical as a danger to the colony and immediately attack their queen as soon as they smell it. However, the process is slow, requiring several disenchantments and many attacks from her workers before the queen is eventually killed. The parasitic queen can then lay her own eggs, which are cared for by the workers.
“If parasitism is successful, it will allow the new queen to go through the vulnerable founding phase much more safely than founding a colony alone,” says Takasuka. “I suspect this strategy may be more common than we currently think.”
Chris Reed from Macquarie University in Sydney, Australia, says complex ant behavior is difficult to observe because it occurs in the privacy of an underground nest.
“Natural history detective work like this is vital to improving our understanding of these incredibly important insects,” says Reed. “Further research may even lead to new ways to control queen invasive ant species, which are one of the biggest challenges facing ecosystems around the world.”
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