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Ants Employ Scorched Earth Tactics to Fight against Spiders

Huntsman Spider

Image credit: Bryce McQuillan via Wikimedia

Well-known for the ferociously attacking with its sting and its jaws at the same time, the bulldog ant called as Myrmecia pyriformis is regarded as “most dangerous ant” in the world. Living in the dry forests of eastern Australia, such ants are the natural enemies of Delena cancerides, the the social huntsman spider, because these two species look for their food in the same places at the same period of time, beginning at twilight and continuing through all the night. According to the report by New Scientist, the ants apply dirty tactics during such turf war.

Instead of weaving webs, the social spiders make their nest under the dead tree’s loose barks. The size of the female could be as big as your palm in terms of her legs and she would lives together her offspring of several generations, whose number could reach a couple hundred. Colonies of bulldog ants could go up to around 1,400.

In ecological sense, interference competition take places if two species bodily interfere with each other aggressively so as to keep the other species away from their habitats or resources. The final result of such kind of competition would be coexistence or exclusion. In order to know whether the interference could cause the partitioning of resources and what would occur when the resource was just necessity to one species, but not the other, Eric Yip from Cornell set up over 100 nest boxes in the field and tried to find out the result.

During the growing period of her offspring, female spiders would spend several months keeping maintenance of her home. However, when bulldog ants fight their way into the nest, as a result, these ants would overwhelm the spider in terms of their ferocity and numbers. Therefore, the female spiders would retreat with her offspring. But the ants don’t care about the occupation of the nest. Instead, they would only fill the nest up with bark, twigs and litter in order to make the nests useless for the spiders and afterwards they would go away.

Of the 120 nest boxes that housed the spiders, seven of them, equaling the six percent of the total number, were taken by the ants during the period of two-months. In the interview with New Scientist, Yip said that in a few cases, the adult female was capable of killing all the ants; however her offspring failed to do so, because their fangs were unable to puncture the exoskeleton of ants.

In most cases, after excluding spiders from the nest boxes, the ants would fill such boxes them with debris before they went away. As it would take up to a year for the spiders to become mature, so they would need space to grow up. Therefore, filling the nest up would be useless. It was found from the study that no nest was reoccupied later.

Journal reference: Yip, E. C. “Ants versus spiders: interference competition between two social predators.” Insectes Sociaux (2014): 1-4.

Image source: Bryce McQuillan (middle), Narendra A, Reid SF, Raderschall CA, PLoS One 2013(middle) via Wikimedia

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