Let’s Talk Bugs
by Tom Lager

I am sure this has happened to you too; you wake in the morning to realize you have missed a significant event. That is what happened on our road trip to Canada last week. Our dawn departure from the motel was delayed as I saw thousands of mayflies covering the vegetation, the road side and other surfaces of convenience near lights that had been lit during the night. These beautiful creatures were Brown Drakes, also known in some circles as Ephemera simulans. During the night it must have been quite a scene as thousands emerged from Lake Michigan and swarmed to the lights. I can imagine a “snow storm” of swirling mayflies; the sound of their wings and the marauding bats driving through the aerial mass. As this went on I slept, totally unconnected, totally unprepared for what His natural environs has given us.

I, like many of you this year, had previously experienced an early Hex hatch on Wisconsin’s rivers and know typically that Brown Drakes precede the Hex. In this case I am certain that Brown Drakes emerge later in the Manistique area (in July) due to being further north and from the influence of cooler lake environment. They were all in the dune stage as is evident in Figure 1; their final molt will occur prior to forming mating swarms over the lake in the subsequent evening. Notice in Fig 1. how similar they all are in orientation – all facing up toward the sky (the picture is oriented 90 degrees off normal for space reasons). On vegetation they arrange themselves in close head to tail orientation in a mix of males and females and again if possible facing up to the sky. The sexes are easily determined since males have large eyes and at the terminal end of a slender abdomen they have prominent claspers. Females conversely have small eyes and large diameter abdomens. These differences have rational explanations; males need good eye sight to capture and clasp females during mating and females need the cargo space for the egg masses they carry.

The Drakes also gathered on the roads and in the ditches (Fig 2); not in numbers enough to cause a slippery surface. In other times and locations safety has been a concern due to large numbers of mayflies coating bridge surfaces. I have pictures of “drifts several feet deep” of mayflies on bridges. The key take away for me on last weeks events is that even if we do not anticipate up-coming events, once observed though take the time to stop and enjoy the sight – even if it means laying on the road for an eye to eye view with mayflies. As a larva, this mayfly belongs to a group called “burrowing mayflies”, typically Hex, White, Green Drakes and Brown Drakes belong to this group. The larva makes a U-shaped burrow in soft silty, sand and mucky stream, river or lake bottoms. They beat their gills thereby causing water to “pump” through the burrow bringing food particles to them and enabling a constant supply of oxygenated water. The types of soft bottoms preferred within this group influences where fishers find these mayflies. For example Hex prefer soft organic mucky flats along rivers and the White mayfly prefer firmer bottoms composed of sandy clay substrates. Knowing stream physical characteristics can guide you to where to expect to find them for their scheduled hatch times.

Remember the trico hatches have been underway for sometime now, get ready for the “white mayflies” (Ephoron leukon) and do not over look the grasshoppers either. As you are having neat experiences with “the bugs” out there let me know how it is going.
 

Fig 1. Early morning formation of Brown Drakes, Manistique MI (July 17, 2006)

Fig 2. Like sail boats Brown Drakes await the warming sun along the road side.