C. umbratica has excellent eyesight that is especially sensitive to UV light, and the males and females have UV-reflective body parts. In UV light the males have fluorescent patches of scales on the face and body; the females have a bright green body part called a palp near the mouth that turns bright fluorescent green. UV light is a natural part of the full spectrum light that comes from the Sun.

    In full-spectrum light, both sexes adopt courtship posturing. However, researchers from National University of Singapore in Singapore and University of Sussex in Britain observed male-female behavior when individuals of one sex were in full-spectrum light and the opposite-sex partners were in UV-deficient light.

    In the experiment, researchers watched the males and female jumping spiders interact under UV light and then used a filter that blocked that part of the light. They found that without their partner being in UV light, females showed no interest. When the females were not in UV, the males ignored the females or responded with less interest.

    The same UV light we try to avoid by using sunscreen and wearing sunglasses, lights up body parts on these jumping spiders, and is critical to their courtship, researchers said.