The Burrowers

The Slit Dwelling Burrowers Families Ephemeridae, Potamanthidae and Polymitarcyidae

The first thing that should be said about the three species of mayfly I chose to research is that both The Hex, and the White Fly are both excluded from the hatch chart I’ve been using and the reason for that is that in this area The Hex and White Fly produce substantial hatch numbers but in the warmer areas of the Mississippi River and the waters flowing into the river. As a result these two will most likely not be trout fly options but I am planning on trying to find these hatches next year and fish for bass or panfish willing to take the large flies. 

With that said the burrowers can be found by sifting through the silt in the stream. With the flowing water easily able to sweep the nymphs through your fingers Hatches 2 suggests bringing a jar that you can fill and shake to stir up the contents to find the nymphs. Burrowers are easily identified by the two large tusks on the head of the nymph. Looking at photo’s one can clearly see the difference between nymphs with and without the tusks.

The Hex (Hexagenia limbata) 6-8 4x Long Tan-Dark Brown Late June-July

The nymphs and indeed duns of the Hexagenia are among the largest of the Mayflies. Note the hook size recommended for the duns of the Hex in 6-8 4x long. What I know of these for this area is that they tend to emerge only on parts of the Mississippi and that a friend of mine fishes this hatch on the river for all kinds of warmer water fish. Hatches 2 gives one hint as to how to distinguish Hexagenia from other burrowers. The other burrowers tend to have deeply forked tusks while Hexagenia have longer more rounded tusks.  The main reason I believe that this is not a source of trout food is that the Mississippi has a better substrate that can allow them to have their U-shaped burrows in 3-6 inches of frim silt. 

Yellow Drake (Anthopotamus distinctus) 10-12 Creamy yellow Late June-Early August

Hatches 2 has this species identified as Potamanthus distinctus. Looking at the nymphs of this species one can easily identify them by the gills that line both sides of the abdomen of the nymph. They are very long and have bristles spanning the distance between them. Tying these nymphs one might consider using very short ginger hackle to represent the gills on the sides, perhaps trimming the top and bottom feathers leaving only the sides. Hatches 2 suggests using a Light Cahill dry pattern in size 10.

White Fly (Ephoron leukon) 8-12 2x Long White Late August-Sept.

The white fly is most likely not going to be a large part of my fly box but I have heard whispers referring to the Ephoron Leukon and in my efforts to be prepared for next year I will not over look this genus of Mayfly. These white mayflies will emerge just after dusk in August and September. On my Dusk til Dawn run near the end of a long day on the water I watched what I thought at first was Ephoron leukon but turned out to be a white caddis fly. Hatches 2 has little to say about this species but all the more reason for me to try and find it next season. 

The Clingers

The Fast Water Clingers Family Heptageniidae

These nymphs all have flat slender bodies, they also all have stronger legs to hold in fast flowing water. All the nymphs except the Epeorus genus have three tails, epeorus having only two. The mayflies that have substantial hatch numbers in S.E. MN are Macaffertium vicarium the March Brown and Macaffertium ithica the Light Cahill. I should note that the names of both of these species have changed from Stenonema vicarium and ithica to Macaffertium after further research demanded the shift in genus. Hatches 2 has them listed as Stenonema.

March Brown (Macaffertium vicarium) 10-12 Mottled tan and brown. June-Mid July

The March Brown is the larger of the two species that in habit Southeastern MN. According to my research the nymphs of vicarium are easily identified by the long tails in addition to the flattened body and strong legs. The tails on vicarium also splay at nearly 90 degrees. These nymphs are on average 16mm in length and are reddish brown. Vicarium move prior to emergence and one should examine rocks in ankle deep fast-moderate water for their presence. One should fish nymph patterns deep near the bottom as these nymphs either crawl or swim close to the bottom to find their emergence site. 

Hatches 2 makes it a point to note that the duns of Vicarium have a wing that slants more than other varieties at a nearly 45 degree angle. Hatching occurs throughout the day from 10am to roughly 6pm during the proper conditions. 

Light Cahill (Macaffertium ithaca) 12-16 Cream to tan. June-Mid July 

There is no picture of an ithaca dun on troutnut.com. I was however, able to find an image of a nymph. It’s interesting to me that troutnut.com has so little information on this species. I will be excited to find samples of these in the wild. 

Hatches 2 clearly states that the nymphs of both varieties here vicarium and ithaca need only be tied in medium and dark brown. Nymphs for ithaca should be tied in size 10-12. I’ve decided that when the mayfly series is over I will be posting a master list with sizes for nymphs and dries as well as color for all species related to S.E. MN. 

Anglers should note that days in June where the weather is cooler due to overcast or rain can produce day long emergence, on hotter days they will be concentrated in the morning. I like the fact that Hatches 2 notes that during this time of the year water levels are usually going down and that you should be careful while wading. 

I like the second image, making me want to try tying nymph with black thread down the hook shank then using perhaps lighter dubbing to simulate the dark center of the nymph.

Note: This information is as region specific (S.E. MN) as I can tailor it to be. It may be relevant to Northern Parts of Iowa and Southwestern Wisconsin. Also, if I forgot something/made a mistake in my information PLEASE post with what needs to be changed. This is for my benifit as well as visitors to W.F.F.

Looking at the 1st nymphal category “The Crawlers” there are five Mayfly species that have direct relevance to myself as well as other S.E. MN anglers. The following is a list in order by approximate hatch dates with condensed versions of relevant information. Thank You Troutnut.com for the excellent pictures.  

The Crawlers

Dark Hendrickson (Ephemerella subvaria ) 12-14 Reddish brown to tan.  April-May

Look for nymphs in the gravel and vegetation of slower meandering water. These nymphs tend to swim for a longer time and can be twitched upon retrieval. Hatching begins at 50-55 degrees. Hatches 2 points out the importance of poor weather slowing the duns down and providing for optimum fishing dun patterns. 

Light Hendrickson (Ephemerella invaria) 12-16 Tan with olive and yellow cast. Late May-June

These nymphs tend to prefer medium-fast water and like subvaria the nymphs use the current to choose an optimum emergence site. So they make for good nymph fishing because they are movin’! Hatching occurs in water from 50-60 degrees. Hatches 2 makes a big point of noting the size and color differences by a hook size or more between invaria, rotunda and dorothea. Meaning to me that I should tie these slightly larger because I’m looking specifically at invaria. 

Iron Blue Quill (Paraleptophlebia) 18-20 Dark gray with maroon cast. Late May-June 

My book says that the hook size for a dry is supposed to be 16-18. The nymphs tend to prefer quieter water. The gills are much larger on these nymphs than those of ephemerella.

Sulfur (Ephemerella dorothea) 16-18 Orange to cream. Late May-Early July

So my research in telling me that dorothea has typical ephemerella features and will spend time finding a spot to emerge. The book really makes a big point to note that dorothea differs from invaria by a full hook size and color. 

White-winged Blacks a.k.a. Trico’s (Tricorythodes) 20-24 Charcoal. July-Sept

I fished during trico action so I’ve seen these and they are small. The book and other info is right on for a 20-24 size hook. The nymphs thrive in streams with a p.h. of 7.5 and above. Nymphs live in the silt, sand and gravel in slow to medium current. As well as the aquatic plant life. Hatching between 52-56 degrees. Trico’s also have typically a very long period of emergence spanning over months.

Trying to keep this short but very useful. Hope my goal is accomplished. Also, I picked dun photos because I’m tying Compara-Dun Dries at the moment. Pictures coming soon.

Looking forward, knowing that the urge is always there, driving by streams because they are out of the way. I have been working on Midges for winter and will continue but in an effort to prepare for the prime season I have been reading up on the Mayfly and in specific the varieties that are of importance to my waters.

The task has been very interesting and makes me wish I had started trout hunting much earlier in the season last year. Seeing naturals will be the best way to talor my flies to what the trout here eat. With out that the best I can do is read. With a few hatch charts for this area I have picked the main species of mayfly in this area to research further.

http://files.dnr.state.mn.us/areas/fisheries/lanesboro/se_mn_hatches_080405.pdf

http://www.troutnut.com/hatch/4/Insect-Ephemeroptera-Mayflies

Hatches 2 is going to be my primary source for specific size and color variations for the species I find in the hatch charts. Along with the specific species they break down into four main categories according to nymphal type.

1. The Crawlers

The Super Crawlers Family Emphemerellidae, The Feeble-Legged Crawlers Family Leptophlebiidae, The Tiny Crawlers Family Tricorythidae and Caenidae

2. The Clingers

The Fast Water Clingers Family Heptageniidae

3. The Burrowers

The Slit Dwelling Burrowers Families Ephemeridae, Potamanthidae and Polymitarcyidae

4. The Swimmers

The Darting Swimmers Families Baetidae, Siphloridae and Metretopodidae.

I like the descriptive terms the book uses to help you remember key information about the characteristics of the real life insect such as “silt dwelling” useful to know where and when you will find these insects on the stream. In posts over the next few weeks I will look at specific species of mayfly in these four categories. It is my hope that posting the important information for my area will help me make much better choices with regards to fly tying. This is how I will prepare for next season without having the experiences I will get next season.