MU biologist Rex Cocroft studies communication, something crucial to life at many levels, as it occurs within a cell, between cells, and between organisms within social groups. "Once we reach the level of communication between individuals," waxes Cocroft, "not only is there the fascinating intellectual challenge of studying communication, but there is also this tremendous aesthetic appeal…. The signals themselves are often beautiful—the songs of whales, the colors of butterfly wings, the scents of flowers." His first calling was that of a musician, so it's perhaps no surprise that Cocroft was drawn to this aspect of biology, and no accident that he enjoys being at MU. "I love it here [in Missouri] in the late summer," he says, "when the katydids and the cicadas are out and there's this din of calling insects."

With the tree-hoppers Cocroft demonstrates how sexual reproduction relies on elaborate communication. The vibrational signals sent through the stems and leaves of plants are “very important in mate choice.”

If the signals of two populations of the same species diverge for some reason, individuals from one group may be less likely to recognize individuals from the other group as mating material – “and these can eventually become separate gene pools, whereas if their signals stay the same they are likely to interbreed. That’s a very strong homogenizing force that can prevent them from differentiating into different species.”

Tree-hoppers are intimately adapted to the host plant on which they live. “Their whole life cycle is timed to the progression of their plant,” explains Cocroft. In the fall they lay eggs in the bark; later, in the spring, the tree’s sap rising triggers the eggs to develop and hatch just as the leaves begin to emerge, providing the nymphs with new growth to eat.