Lets Talk Bugs
by Tom Lager

The water temperature was a fraction above 32º F in the Oconto River this weekend. At least, that is what my thermometer indicated. What were we doing there? At times the need to explore "running water" is too much to resist – rivers are beautiful places where we learn through observation or at times we are just "with the river" and we let the river talk. That was how is was this time, the heavy snow fall muffled sounds, except for the quietness of its flow that had melted a wide passageway through surface ice.

The rocks and wood from the river were not bustling with life, in fact those bugs present were quite sluggish. They moved in slow motion much like my fingers after being in water for just minutes. Midges, caddis and the like were carrying on doing their thing. What was not obvious, probably, was the most interesting. Those bugs that were absent from the surface were waiting for warmer weather in the months to come.

While walking on the gravel and among the rocks, we are actually walking over a substantial part of the bug community, since many migrate into the substrate of the river. They occupy the interstitial spaces within the river bed where water flows through the beds of gravel and rock. Certainly many of these are small in size and represent early life stages of those we commonly see in spring. We all understand the importance of good flows through gravel beds for successful hatching of trout eggs. The same is true for bugs, not only as eggs but, also their young life stages.

Figure 1. Stonefly larvae typical of those inhabiting stream hyporheic zones.

Another reason I think bugs inhabit this hyporheic zone (a little jargon, if you please) is that temperatures are stable, being warmer in winter and cooler in summer. Actually, summer cooling is likely more important to survival of temperature sensitive insects like larval stoneflies. Some have been found in excess of a meter deep in the substrates of rivers, where temperatures will be near 50 F.

So as I walk along on the shelf-ice back to where Mr. President is casting into a deep run, I am reminded that the apparent quietness of the river belies what actually flourishes within its depths — another example of how the Designer created for us a resource worth our efforts to preserve it.

We did not see the real objective of our trip, at least the one we used for an excuse for the trip, but we noted evidence enough to know we'll be back soon. Hopefully, you will also find time to check out the browns and take the time to turn a few rocks over and look at the bugs