SMART NEWS

Some Spiders Eat Salads

Most people think of spiders as terrifying carnivores, laying in wait to trap their prey. That’s mostly true, but sometimes spiders eat other things too

Rose Eveleth

Contributor

December 24, 2013

Most people think of spiders as terrifying carnivores, laying in wait to trap their prey and mercilessly devour them. That's mostly true, but sometimes spiders eat other things too. Like pollen, apparently.

In a recent study, researchers wanted to figure out whether orb weaver spiders were eating the pollen that got stuck to their webs. To figure that out, they did a pretty basic experiment: catch some spiders, put them in a cardboard box, have them make a nest and sprinkle that nest with pollen. Elizabeth Preston at the blog InkFish explains what happened next:

After a month, Eggs broke down the spiders' bodies and examined the carbon and nitrogen isotopes inside them. Isotopes, if it's been a while since your last chemistry class, are different forms of the same element. For example, most carbon atoms in the world have 6 protons plus 6 neutrons in their nuclei, making them carbon-12. But a small percentage of carbon atoms, called carbon-13, have an extra neutron. Animals incorporate the atoms they eat into their bodies. So by comparing the ratio of lighter to heavier isotopes in spiders' bodies to the signature ratios of their various foods, the researchers could see what the spiders were eating.

But would the spiders do the same thing outside the lab? To find out, the scientists gathered orb spiders from outside and performed the same isotope analysis. What they found was that about 25 percent of the orb weaver's diet was made up of pollen.

Preston points out a few reasons why spiders might eat so much pollen. Orb weavers often eat their webs to recycle the silk, and they might as well eat the pollen on there too, especially in lean times when insects to eat are hard to find. Perhaps it's time to take on the strategy of the spider, and start the "orb weaver spider diet"—75 percent insect, 25 percent plant.