Environmentalists worry about pollinating species in the pivotal desert borderland as more tall barriers are planned by the U.S. government to curb migration and trafficking.By Tina DeinesIt was a balmy day in Del Rio, a Texas border town about 170 miles west of San Antonio, when a citizen conservationist looking for wildlife stumbled upon a striking rust and orange caterpillar with fleshy horn-like protrusions that are meant to scare predators.