The paper covers were then taken off and transferred to another set of branches. This set had already been explored by another ant colony, which found a tasty meal of sucrose at the end of the trail.
Even though the food reward was still there, ants performed a U-turn or chose another direction whenever they came across the covers.
The team concluded that the ants use a repellent pheromone to mark unrewarding branches at "decision points," where branches fork.
"It provides advance warning, like human road signs situated before junctions," the authors suggest.
In a study published last December, the same team found that Pharaoh ants deposited pheromones wherever the trail forked at 60 degrees. The markers are like invisible signposts, helping ants to find their way home.
The latest finding amplifies this, showing that the ants also use scent as a negative signal to help them in their quest for food.
Name: Pharaoh Ant (
Monomorium pharaonis)
Primary Classification: Formicidae (Ants)
Location: Worldwide (likely native to Africa)
Habitat: Human dwellings
Diet: Sweet and fatty foods
Size: From 1/12 to 1/16 inches in length
Description: Yellowish, light brown or red in color; dark or blackish abdomen; long, segmented antennae; comparatively small eyes
Cool Facts: It is called the "pharaoh ant" because it was once mistakenly identified as one of the plagues of Ancient Egypt. It has the dubious distinction of being the most difficult household ant to get rid of, resisting most types of pest control treatments.
Conservation Status: Common
