Cross your fingers for clear skies, space fans: A partial solar eclipse will grace the skies on Thursday afternoon over most of North America. According to NASA's predictions, the moon will pass between the Earth and the sun and cast a shadow that will obscure up to 81 percent of the yellow star.
If you're planning on gazing at the sun, you've hopefully prepared by gearing up with filtered telescopes, binoculars, viewfinders, or—if you're handy—pinhole projectors. That's the human reaction to an eclipse: get out the telescope and start looking.
The rest of the animal kingdom seems less interested in studying the sun. It's not that animals don't notice these kinds of eclipses—they certainly do, and some may be far more sensitive than humans to them. But their responses to the darkening sun tend to be less about curiosity and wonder, and more about survival.
Among insects, desert cicada have been found to be particularly sensitive to partial eclipses. In the summer of 1991, researchers at the University of Illinois and Florida's Barry University traveled to Arizona to observe cicada behavior. A partial solar eclipse happened to occur while they were there, and they observed whether cicada behavior changed, discovering the following:
On the day of the eclipse, Diceroprocta semicincta (Davis) and Cacama valvata (Uhler) began calling in Tucson before 8:00 AM and were calling normally as the eclipse began, at 10:15 AM. Soon after the coverage of the sun had reached approximately 50%, the cicadas ceased calling. The interruption in calling continued for about 40 min during the eclipse; about 20 min on each side of the maximal eclipse.
In other words, they all went silent when a few degrees lowered under the eclipse's shadow. That's because the cicada's call is energy intensive, and the researchers think that below a certain temperature it becomes impossible for the bugs to maintain the body heat they need to sing.