Terrestrials are insects that live on land and make the mistake of falling into the water for trout to devour. Insects like the grasshopper, beetle and ant fall into this category. Most terrestrials are prevalent in the late summer or early fall. As the winds pick up and farmers cut hay or grass these insects take flight and if near a river or stream end up as food. Terrestrials are normally fished on top and many flies are tied with foam to keep them afloat. When fishing these flies don’t try to set them lightly on the surface like you would a mayfly or caddis. Go ahead and give them a smack on the water to let the trout know that they have arrived.