The protector species, the weaver ant Oecophylla smaragdina, can also turn predator of the associate species, the jumping spider Phintella piatensis.

Scientists have recently observed a timid jumping spider (Phintella piantensis) that makes its nest in a curiously dangerous place, in close vicinity to the nests of weaver ants (Oecophylla smaragdina), which prey on the spider.

They do this in order to protect themselves from another spider which likes to eat them — a predatory spitting spider in the genus Scytodes — because the predatory spider is repelled by the specific airborne olfactory compounds that the ants release.

In other words, the jumping spider uses the scent of the ants as a secret weapon to save itself from becoming the prey of the predatory spitting spider. The downside to this plan is that jumping spiders are also a favorite snack of their saviors. To overcome this additional hazard, the spider has made yet another plan in the form of an ant-proof nest, writes Ximena Nelson of the University of Canterbury in New Zealand and Robert Jackson of the University of Canterbury and the International Centre of Insect Physiology and Ecology in Kenya, in the journal Behavioral Ecology and Sociobiology.

The jumping spiders build dense ant-proof nests of an unusually tough and dense weave that are difficult for the insects to tear open. The nest’s hinged flaps of silk at each end function as swinging doors. The spider quickly raises these when it enters or leaves the nest, before any ants can follow, too.

The researchers found that jumping spiders choose nesting sites based on whether they can see active living ants, if they detect ant odor or can see mounts made from dead weaver ants. Thus, they are protected from the predatory spider by the scent of the ants, and they’re protected from the ants by the construction of their nests.

“Nesting associations with territorial ants whereby the ant does not receive any benefit may be more common among arthropods than is currently appreciated,” concludes Nelson. “We expect that a closer look at ant-other arthropod relationships will yield numerous examples similar to ours and provide a better understanding of the complexities of microhabitat choice and its ecological ramifications.”

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– Timid spider uses odor and visual cues to actively select protected nesting sites near ants