The mottled brown insects ranged from puny little quarterinchers that hardly seemed to merit the lengthy scientific names recorded on the outside of their vials to whopping behemoths that threatened to push the alcohol soaked cotton wads clear out. Kathleen Walsh clipped off portions of the stoneflies' wings, treated them, and embedded them in individual blocks of resin. Then, using a scanning-electron microscope, or SEM, she brought their tiny tubelike wingvein structures into vivid view. Until recently scientists had no explanation for how swimming critters managed to leave behind their waterbound lives and take to the air. Then in 1994, Penn State biologist James Marden and then-undergraduate Melissa Kramer published a paper in the journal Science about their work with stoneflies.
Skimmers come in three different types.
Gusts of wind push him along. The second one flaps his wings. The third one goes up on his hind legs and skims across the water. All of them move above the surface of the water, but they rarely fly. That's why Marden thought it was a good order to look at for the evolution of flight.