Sometimes Spiders Go Vegetarian, Scientists Find

The Maevia inclemens is one species of jumping spider witnessed feeding on plant material. Thomas Shahan/Flickr

Think of how a spider feeds. Chances are, you're imagining an insect caught in an intricate web woven by the arachnid. Maybe the spider's wrapping up a wasp in silk for later, or maybe it's chowing down on a fly. Either way, spiders are generally thought of as predators —  larger spiders even hunt large animals like birds and fish. But a new investigation by zoologists has shown that the eight-legged creatures sometimes draw sustenance from a vegetarian diet, too.

A recent study in the Journal of Arachnology chronicled 95 instances of spiders turning to plants for nutrition, consuming floral nectar, plant sap, seeds, pollen, honeydew and other parts of plants. The examples spanned more than 60 arachnid species and 10 spider families across the globe, and showed spiders gaining nutrition from more than 20 different families of plant, from tree to grass to orchid.

A Plexippus jumping spider in covered in hibiscus pollen.
Nick Hobgood/University of South Pacific

"The ability of spiders to derive nutrients from plants is broadening the food base of these animals," says lead author Martin Nyffeler, of the University of Basel in Switzerland, in a press release. "This might be a survival mechanism helping spiders to stay alive during periods when insects are scarce. In addition, diversifying their diet with plant is advantageous from a nutritional point of view, since diet mixing is optimizing nutrient intake."

The scientists noted spiders drawing nutrition from plants on every continent except for Antarctica, though it happens more frequently in warmer temperatures. Whether this is a common occurrence, and to what degree plant sources contribute to spider nutrition, is largely unknown. So if you're a budding scientist looking for a new field of study and you've got a passion for both creepy crawlies and veggie snacks, you're welcome — here's your dissertation topic.

A juvenile Baheera kiplingi jumping spider eating a detachable leaflet tip of an acacia tree in Mexico.
Eric J. Scully, Harvard University
Golden-tailed spiny ants in Australia defend a source of plant nectar from a Cosmophasis micarioides spider trying to access the food.
Andrea Lim, James Cook University