By Gail Ellis  STILLWATER, Okla. – Like a total eclipse of the sun or rare blood moon, the mass emergence of periodical cicadas is a natural phenomenon that piques interest worldwide. While the 17-year cicada is crawling aboveground now on the East Coast and in the upper Midwest, state Extension specialists say Oklahoma is in the clear.  Eric Rebek, Oklahoma State University entomology professor and Extension specialist, said the Brood X species of periodical cicada making headlines this summer is…