Spiders Cannot Physically Chew Their Food

A spider's meal is a process of external digestion, a fascinating evolutionary adaptation for a predator (Review) with a gut too narrow for solid food. Unable to chew, spiders instead release digestive fluids onto or into their prey. These potent enzymatic cocktails, rich in proteases and lipases, break down the prey's tissues into a nutrient-rich slurry. This method allows spiders to consume prey that is often much larger than themselves. Some spiders will use their fanged mouthparts, or chelicerae, to mash their victim while flooding it with these enzymes, while others simply inject the digestive liquid and wait for the insides to liquefy.

This unique feeding strategy is an ancient one, with evidence suggesting a shared evolutionary origin between digestive enzymes and the toxins found in spider venom (Review). Once the prey's internal structures have been sufficiently broken down, the spider uses its sucking stomach to ingest the liquid meal. The entire process can be time-consuming, which is why many spiders will tightly wrap their captured prey in silk. This isn't just for storage; the silk wrapping effectively restrains the meal, ensuring it doesn't escape while the external digestion takes place.

The result of this elaborate process is an empty husk, as the spider has consumed all the digestible soft tissues. This highly efficient system allows spiders to extract the maximum amount of nutrients from their food. From the venom that subdues to the enzymes that dissolve and the silk that secures, a spider's feeding habits are a remarkable example of evolutionary innovation in the animal kingdom.