The Elements of Evolution (43-15-11) Beltian Body Snatcher

  Beltian Body Snatcher

At least one spider doesn’t swear by silk to get fed. The acacia jumping spider is largely vegetarian.

The acacia spider has an especial fondness for Beltian bodies: nutritiously rich nubs that form at the leaf tips of an acacia tree. The Beltian bodies are intended as payoff for acacia ants, which the tree feeds in return for protection from herbivores that are more of threat to them than the jumping spider.

The spiders live out on the tips of old leaves, where ants seldom go. To feed, they head in to newer leaves. The ants diligently defend their Beltian body food supply, so a filching spider has to be stealthy and swift.

A spider waits for an opening, then darts in. It clips off a Beltian body, holding the morsel in its mouth as it makes its getaway. Once back on an undefended part of the plant, the sneaky spider enjoys its booty.

Acacia spiders have keen eyesight, are especially fast and agile, and likely possess considerable cognitive skill. Stealing from a colony of ants right under their noses is one snappy trick.

The interdependence between ants and acacias allowed for the emergence of the Beltian body. Now the only known case of spider herbivory depends on this interdependence. ~ American biologist Christopher Meehan