Original: Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight.
Simplified: The placement of the web allows different spiders to trap different insects in the same area. Flat, horizontal webs allow them to trap insects that fly up from vegetation underneath, for example. Flat vertical nets allow them to trap insects in flight.