In Latin America lives a unique spider Bagheera Kipling. This is a jumping spider, he, like the whole group, has large keen eyes and an amazing ability to jump. But he also has a trait that makes him stand out from the 40000 species of spiders – he is almost a vegetarian.
Almost all spiders are predators. They can hunt using various methods, but in the end they all suck out the liquefied internal organs of the victim. If they do consume plants, it is rare, almost accidental. Some may sip nectar from time to time to supplement their meat diet. Others accidentally ingest the pollen while recycling their webs.
But Kipling’s Bagheera is an exception. Christopher Meehan of Villanova University found that spiders use the partnership of ants and acacia. Acacia trees use ants as protectors and provide them with shelter in hollow thorns and tasty growths on their leaves called Belt corpuscles. Kipling’s baghears learned to steal these delicacies from ants, and as a result, became the only (almost) vegetarian spiders.
Mian spent seven years observing spiders and how they get food. He showed that spiders can almost always be found on acacias where ants live, because Belt corpuscles grow on acacias only in the presence of ants.
In Mexico, the Belt bodies make up 91% of the spider’s diet, and in Costa Rica, 60%. Less often they drink nectar, and even more rarely they eat meat, eating ant larvae, flies, and even members of their own species.
Meehan confirmed his results by analyzing the chemical composition of the spider’s body. He looked at the ratio of two isotopes of nitrogen: N-15 and N-14. Those who eat plant foods have lower levels of N-15 than meat-eaters, and Bagheera Kipling’s body has 5% less of this isotope than other jumping spiders. Meehan also compared the levels of two carbon isotopes, C-13 and C-12. He found that in the body of a vegetarian spider and in Belt bodies, there is almost the same ratio, which is typical for animals and their food.
Eating belt calves is useful, but not so easy. First, there is the problem of guard ants. Bagheera Kipling’s strategy is stealth and maneuverability. It builds nests at the tips of the oldest leaves, where ants rarely go. Spiders actively hide from approaching patrols. If cornered, they use their powerful paws to make a long jump. Sometimes they use the web, hanging in the air until the danger has passed. Meehan has documented several strategies, all of which are proof of the impressive intelligence for which jumping spiders are famous.
Even if Kipling’s Bagheera manages to escape the patrol, there is still a problem. Belt bodies are very rich in fiber, and spiders, in theory, should not be able to cope with it. Spiders cannot chew food, they digest their victims externally using poison and gastric juices, and then “drink” the liquefied remains. Plant fiber is much tougher, and we still don’t know how Kipling’s Bagheera handles it.
In general, it’s worth it. Belt corpuscles are a ready source of food available all year round. Using other people’s food, Kipling’s Bagheeras have prospered. Today they can be found everywhere in Latin America, where ants “collaborate” with acacias.