Trail Marker 4 | National Institute of Environmental Health Sciences Skip Navigation Close the left navigation You Are Here View the Full Map Trail Marker 4 In the distance, plant succession, or a change in the types of plant species that occupy a given area, is taking place, with native grasses taking over a formerly mowed area. This area, mowed once a year in October, allows the annuals and perennials to grow and flower. A Purple Martin house is located in the background. Martins are capable of catching insects above the treetops. Contrary to popular belief, they don’t eat mosquitos — bats have that responsibility. More about the martin More about the bat Where To Next? Previous | 3 Next | 5 Back to Top Last Reviewed: December 19, 2025