What should we call a Texan ant that rides on the backs of other ants? Rodeo ants, says Alex Wild at the University of Texas at Austin, who has discovered two new species of such insects.
While little is known about them 鈥� so far, Wild鈥檚 team has found just one individual from each of the two species 鈥� a few other ant species elsewhere in the world are also known to perch on the backs of other ants.
In those cases, the 鈥渞iders鈥� have evolved an unusual way of life. Most ants live in huge colonies with one egg-laying queen and millions of sterile workers that bring food home to the nest and tend to the eggs. The riders don鈥檛 have any workers: they are females that cling to the back of a queen from a bigger species. The riders lay their own eggs and fool the larger queen鈥檚 workers into looking after them.
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The two newly discovered Texan species most likely live in the same way, says Wild. 鈥淪he鈥檚 probably dropping her own eggs into the brood pile, where the host workers are treating them as their own. She鈥檚 a parasite on the food and labour of the host colony.鈥�
They seem to have adapted their appearance and behaviour to their freeloading lifestyle. Each has a similar density of hairs on their back to their host ant, as if to blend in.
Although one was killed on collection, Wild was able to observe the second in the lab for some time, and when he repeatedly detached it from the larger ant, it kept climbing back on. 鈥淭hey really like being on the queen.鈥�
The rodeo ants may also avoid being detected by covering themselves with chemicals secreted by the host queen, as some other ants that enter the nests of others do, says Nigel Franks at the University of Bristol, UK, who wasn鈥檛 involved in the work. 鈥淚t鈥檚 a brilliant strategy.鈥�
Wild presented the findings at the Entomology 2019 conference in St Louis, Missouri, last month.
