

Spiders mostly eat insects, although some of the larger species have been known to snack on lizards, birds and even small mammals. Given their abundance and the voraciousness of their appetites, two European biologists recently wondered: If you were to tally up all the food eaten by the world's entire spider population in a single year, how much would it be?





To arrive at this number Nyffler and Birkhofer did a lot of sophisticated estimation based on existing research into A) how many spiders live in a square meter of land for all the main habitat types on Earth, and B) the average amount of food consumed by spiders of different sizes in a given year.

These numbers yielded some interesting factoids on their own. For instance, one study estimated that global average spider density stands at about 131 spiders per square meter. Some habitats, like deserts and tundra, are home to fewer spiders. On the other hand, spider densities of 1,000 or more individuals per square meter have been observed under certain “favorable” conditions — since Nyffler and Birkhofer don't define what “favorable” means in this context, I'm going to assume it refers to dark, dusty places like the area under my bed.


If you gathered up all the spiders on the planet and placed them on a very large scale, together they'd weigh about 25 million tons, according to Nyffler and Birkhofer. For comparison, the Titanic weighed about 52,000 tons. The mass of every spider on Earth today, in other words, is equivalent to 478 Titanics.

Spider biologists have also generally found that spiders consume approximately 10 percent of their body weight in food per day. That's equivalent to a 200-pound man eating 20 pounds of meat each day.


In the end, spiders' voracity actually works out to mankind's benefit. Since they primarily feast on bugs, their hunger means fewer pests in the garden, fewer mosquitoes in the yard and fewer flies in the house.

The Washington Post reached out to a spider for comment on this story. Its reply: