The female of the species has a leg span of up to 5 inches (12 centimeters), while the male—which spends much of its time clambering on its partner's back—barely reaches an inch (2.5 centimeters), a new study says.
Part of a well-known group of golden orb-weaver spiders—which can spin webs up to three feet (one meter) wide—N. komaci was first identified in a South African museum collection in 2000.
But it wasn't until a 2007 field survey, which discovered three individuals in South Africa's Tembe Elephant Park, that scientists knew the spider still existed in the wild.
The newfound spider, detailed October 20 in the journal PLoS One, is the first addition to the Nephila genus since 1879.
Largest Web-Spinner a Rarity
N. komaci is likely rare within its small habitats in South Africa and Madagascar, researchers say, and females are much less common than males.
Much is still unknown about the species' biology, but study co-author and spider expert Jonathan Coddington suspects the female evolved her extreme size to thwart smaller predators and to be able to lay more eggs.
In addition, the males are "sort of fanatically monogamous" during their roughly one-year life spans, said Coddington, a senior scientist at the National Museum of Natural History in Washington, D.C.
When ready to mate, a male will usually make his move when the female is molting, he added.
"Her legs are soft and her body's soft, and she can't prevent being inseminated by the male," Coddington said. "Once he's inseminated her, he'll break off his genitalia in hers, thereby plugging her up."
The male, which is left sterile, then drives away other males until he dies.
This strategy should stymie other males' mating attempts—though some females have been found with several dismembered male organs lodged inside them, he said.
Overall, Coddington added, the discovery of this new species is "just further evidence that it's a wonderful world."