Ferociously attacking with its sting and its jaws simultaneously, the bulldog ant Myrmecia pyriformis holds the world record for “most dangerous ant.” And in the dry forests of eastern Australia, the ants are the mortal enemies of the social huntsman spider, Delena cancerides.
The two species forage at the same time -- starting around twilight and
lasting throughout the night -- in the same places. And in this turf
war, these ants fight dirty, New Scientist reports.
Rather than weave webs, the social spiders nest under the loose bark
of dead trees. Females can grow to the size of your palm (mostly legs
though), and she lives together with several generations of her
offspring, which adds up to a couple hundred individuals. Colonies of
bulldog ants can reach 1,400 strong.
In ecology, interference competition is
when two species physically interfere with one another by aggressively
trying to exclude the other from habitats or resources. This type of
competition often leads to either coexistence or exclusion. But does
interference lead to a partitioning of resources? And what happens if
the resource is only necessary to one species, but not the other? To
investigate, Eric Yip from Cornell set up over 100 nest boxes in the field and watched what happened.
Female spiders spend months maintaining the home while her offspring
grow. But when bulldog ants battle their way into the nest, their
numbers and ferocity overwhelm the spider and she retreats with her
young. But the ants don’t even want to occupy the nest. They just fill
it up with twigs, bark, and litter -- making the nests useless for the
spiders -- and then they leave.
Of the 120 nest boxes that were colonized by the spiders, seven of
them (that’s six percent) were invaded by the ants over a two-month
period. "In a couple of instances the adult female was able to kill all
the ants," Yip tells New Scientist. But her offspring couldn't because "their fangs can't puncture the ant exoskeleton."
Most of the time, after eliminating spiders from the nest boxes, the
ants filled them with debris before leaving. Since the spiders, who can
take up to a year to mature, need space to grow, filling the nest up
renders it useless. None of the nests were reoccupied during the study.
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