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Meet the Golden Orb Web Spider

Ambika Kamath | Updated on September 12, 2014 Published on January 25, 2014

Trap dancing: A Nephila spider at work in Florida. Photo: Ambika Kamath

Spider crawling-col.eps

Eating a willing mate, fending off ant attacks, trapping bees... these super spiders are incy, wincy, invincible

Spiders are perhaps not your favourite creatures — along with snakes, spiders are more reviled than any other animal. But suspend your emotions temporarily, while I convince you that spiders are more interesting than scary by introducing you to the Golden Orb Web Spiders or Nephila, as they are known scientifically. Nephila are found all across the tropics, including India. When you encounter a Nephila web, you’ll be struck by two things — the size of these spiders and their immense, golden webs. Both of which are great entry points to the exciting world of spider biology.

In many animals, males and females differ in size. In most examples one can think of, males are often bigger than females — humans, peacocks, garden lizards and so on… However, the land-dwelling species with the biggest size difference between sexes is none other than Nephila. Female Nephila can be up to 500 times as heavy as males — that’s comparable to the difference in weight between you and a potato.

This dramatic size difference makes reproduction somewhat daunting for male Nephila, especially when you consider that female spiders often eat their male counterparts. How could this situation, where half of a species regularly cannibalise the other half, be stable? It boils down to timing. If a male gets eaten by a female after mating, being eaten is actually beneficial to the male too — by supplying nutrition to the female, he indirectly gives his own offspring some extra food and a head start in life. (Hey, we’re trying to be positive here).

The complexities of eating and being eaten also affect how Nephila interact with ants. When I imagine a contest between an ant and a spider, the outcome is obvious — the spider will win, of course. But what about a spider versus an army of ants? Even spiders as big as Nephila, which can be larger than the palm of your hand, worry about being attacked by ants. These spiders have therefore evolved a way to prevent ant attacks by coating their silk with a chemical that ants find repulsive. But the downside of this defence is that Nephila webs drive away non-threatening ants as well, perhaps, failing to capitalise on an important food source. It appears that, in this case, the fear of being eaten trumps the need to eat.

Yet Nephila have evolved other ways of luring insects towards them. Glowing in the sunlight, Nephila webs can be a lovely golden colour. This colour is crucial to the trap set by Nephila for nectar-feeding bees. Many bees have an innate preference for yellow, a preference that is co-opted by flowers, and also Nephila webs, to attract bees towards them. Unlike their relationship with flowers, the interaction between bees and spiders is decidedly asymmetrical — a sticky demise for the bee and a tasty meal for the spider. Yet bees are unable to learn to avoid yellow webs, even when they narrowly escape being caught in them. From the bees’ perspective, the risk of being eaten by a spider pales in comparison to the benefits of feeding on the nectar of yellow flowers.

Like any creature, spiders are part of a web of interactions that, when traced, uncover the intriguing biology of many different organisms. So next time you spot a spider, consider quelling your fear, and focus on this many-legged creature’s role in the vast natural world around you.

This is a monthly series on animals you may have never met, but must (at least, on page).

( Ambika Kamath studies organismic and evolutionary biology at Harvard University.)

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Published on January 25, 2014
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