To date, some 40,000 species of spiders have been recorded worldwide. All of them have a carnivorous diet consisting mainly of insects and small arthropods. All of them, or almost all of them.
A small, eight-legged creature found in Latin America is mainly vegetarian. The species is called Bagheera kiplingi after the famous black panther character in Rudyard Kipling's TheJungle Book. It was first described at the end of the 19th century, but it was not until a hundred years later that its herbivorous tendencies came to light.
A rather cute bug
B. kiplingi belongs to the largest family of spiders, the Salticidae (also known as jumping spiders), which comprises some 5,000 species. Arachnophobes, there is no need to panic. These are far from being the most intimidating creatures. With their tiny legs and large eyes, they can even be downright cute.
Present in Latin America, from Mexico to Costa Rica, B. kiplingi is rather discreet and for good reason, its body does not exceed ten millimetres. This is barely the size of our pinkie nail. It is very colourful and has what is known as sexual dimorphism. In other words, the male and female do not look the same.
While the first has amber legs and green shades on the cephalotorax and abdomen, the second has brown shades. This is enough for both of them to go relatively unnoticed in the middle of the vegetation, especially on the acacias where the species spends most of its time.
This brings us back to its particularity. The Latin American spider is currently the only one in the world known to have a mainly herbivorous diet. Other species have already been observed consuming plants or nectar. But this is always done occasionally (or even accidentally) as a supplement to a carnivorous diet.
Vegetarian and pilferer
Research has shown that it feeds mainly on 'beltid bodies,' the growths on the tips of the leaves of certain acacia trees. According to a 2009 study, these make up 91% of the species' diet in Mexico.
With such an appetite, there's no need to turn into a big predator to feed. The spider must nevertheless be ingenious. For these Beltian bodies are not defenceless. They even have a bodyguard of ants that fiercely protect the plant from any potential herbivore intrusion.
A plant-based meal... sometimes with prey
At present, scientists do not know how and why this species evolved to adopt such a diet. The beltid bodies contain sugars and proteins but are also rich in fibre and low in fat, which normally makes them poor substitutes for prey for a carnivorous animal.
It is important to note that the spider is not an exclusive vegetarian either. The same study showed that in Costa Rica, Belgian bodies constitute 'only' 60% of its diet. It may supplement its diet with nectar, but it also sometimes turns to real prey such as acacia ant larvae, small flies and, more rarely, small congeners.
In any case, this diet seems to be quite successful for B. kiplingi. In 2009, scientists came across an extremely abundant population in a region of Mexico. The pilfering spiders were present on more than 50% of the acacias.