This Spider Spins the World’s Largest Webs — Then Eats Them

Have you ever heard of a spider that eats its own web? Chances are, you probably haven’t, but that is what Darwin’s bark spider is famous for. These spiders eat their own silk to produce more later, recycling the proteins needed to make it. This video by WildEarth shows a female bark spider doing just that. Find out more about this fascinating spider species.

About the Bark Spider

Darwin’s bark spiders are native to Madagascar, where they are most commonly found, though there have been occasional reports of related species or populations in nearby regions. In Madagascar, they inhabit rainforests, rivers, and lakes, building their webs across rivers and streams, specifically because these locations are great places to catch prey. The water hosts several flying insects that the spider can catch, making it the ideal place to hunt.

These spiders exhibit sexual dimorphism, meaning that the characteristics distinguishing males and females are drastically different. For example, females are much larger than males, measuring around 0.8 inches and 0.25 inches, respectively. This is because females are responsible for spinning large webs to catch prey, while males are more mobile for seeking out mates and food.

Their webs are complex marvels of nature. In fact, these spiders have the largest orb webs of any spider species. The webs can be spun up to 80 feet as they stretch across rivers. There are a few other factors that make their webs unique as well. While most spiders build their webs from a central point, the bark spider first creates a long line connecting the two sides of the river, then constructs the web below this line. This bridge allows the spider to cross to either side of the river quickly, all while passively catching food for later. Their webs are also extremely strong, requiring significant force to stretch or break. This is due in part to a special protein called MaSp4, along with other silk proteins, that together give the silk its remarkable strength. These strong webs require a lot of energy, leading the spider to recycle them by eating the silk.

Eating Their Own Webs

Similar to other spiders, producing the silk needed for webs is energy-intensive. The process is metabolically expensive, and bark spiders require more energy than most other spiders to make their silk strong enough. To compensate for the energy and proteins lost when producing silk, the spiders will eat their old silk to prevent wasting nutrients. This typically happens when the spider wants to build a new web after successfully hunting with one. After getting the most out of their web, they begin to consume the silk, allowing the spider to build a new, strong web quickly without expending excessive energy to synthesize new silk.

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