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The discovery is important to science because before this discovery scientist only knew of a few species of animals within birds, fish, mammals, insects, and crustaceans that could see ultraviolet A (UV-A) light.

And, they suspected that no species could see UV-B because of its energetic state: shorter wavelength (and larger frequency), which means it has more energy.

That is: Energy (E) equals [Planck’s Constant (h) times speed of light (c)] divided by wavelength (λ) – or – Energy (E) equals Planck’s Constant (h) times frequency (ν).

However, this discovery shows that at least one species can detect UV-B light. And, if one species can see it, it increases the possibility that other species can also detect UV-B light.

The Li team studied twenty male spiders in glass cages containing light filters. Next to the males were cages full of female spiders.

While observing both groups of spiders the researchers found that the female spiders spent more time watching males perform mating display when UV-B light was allowed to enter the cages (rather than when it was blocked out).

The researchers then used female and male spiders that showed interest in each other. Each pair was placed in a cage that was separated by a filter.

When the UV-B light was blocked (and only visible light was allowed to enter), eleven of the fourteen females did not respond to the mating actions of their male partner.

In all, the researchers performed a series of six experiments. They stated, “By performing six series of binary mate-choice experiments in which we varied lighting conditions with filters (UVB+ [no filter] versus UVB−, UVB+ versus ND1, UVB+ versus ND2, UVB− versus ND1, UVB− versus ND2, and UVB− versus UVA−), we show that significantly more UVB + males than UVB− males are chosen by females as preferred mates. Female preference for UVB-reflective males is not affected by differences in brightness or by UVA.”

The researchers concluded that the physical actions of the males did not attract the females. Instead, the attracting device was the presence of the UV-B light.

The results of the study (“UVB-Based Mate-Choice Cues Used by Females of the Jumping Spider Phintella vittata”) were published online on May 1, 2008, in the journal of Current Biology.

Besides, Li, the research team includes, Zengtao Zhang, Fengxing, Liu, Zingging Liu, Wenjin Gan, and Jian Chen, all from the College of Life Sciences, Hubei University (Wuhan, Hubei, China); and Matthew L.M. Lim, from the Department of Biological Sciences, National University of Singapore (Singapore, Republic of Singapore).

The researchers are planning next to find out how the spiders see the UV-B light and how their eyes are not damaged by the UV-B light.

The research performed by the Li team is a first step in learning more about UV-B light and how other species of animals might respond to it with respect to communications, reproduction, and other facets of their lives.