There are more species of beetles living nearby the typical trout stream than any other terrestrial insect. One reason is that there are more species of beetles than any other insect, period. They fall into the water from the banks, bushes and grass along the banks as well as the limbs of overhanging trees. One of the most common species found along trout streams is the Japanese Beetle. They can are a major food for trout, especially during the hot summer months when there are few aquatic insect hatches. Like most of the other terrestrial insects, you may encounter these insects up until the time it begins to frost.