A spider that surprises, predictably

All spiders, with one known exception, are carnivores. That exception is Bagheera kiplingi, a jumping spider whose relatives seem quite normal, but which has taken up a mostly vegetarian lifestyle. It does this by eating the nutrient-rich Beltian bodies on acacia trees that are tended by ants. If you Google “Bagheera kiplingi”, you’ll find references to studies by Christopher Meehan and colleagues.

The last time I saw the species live was in 1983, and following its fame I wanted to see it again. When Heather spotted a bullhorn acacia as we were driving near San Mateo, Jalisco, we decided to stop the car for a moment. Without even opening the window, I saw a Bagheera kiplingi crawling on the plant. Woohoo! Here are a male and female that we found.  The female has normal jaws that hang down from the face, but the male has jaws (chelicerae) that stick forward, instead of down.

There’s a thrill I get when past scientific work yields a prediction that works. On a little road in Jalisco, nature was in order, with Bagheera and ants and acacia all living together.

As thrilling as it was to find Bagheera kiplingi, there was a cost, as Heather recounts in her blog post about Gasteroposting.