Overview of the Mayfly Species on Northern Wisconsin Trout Streams

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At a much younger age while studying the various mayflies that hatched on my favorite northern Wisconsin trout streams I put together chart in a notebook to help me remember some of the important characteristics for the most common mayflies that I frequently saw hatching. Below I have reproduced the chart in an HTML table and updated the mayfly genus and species names to their current common and scientific names, as of 2012. Hopefully, you will find this mayfly chart beneficial in your pursuit to be more knowledgeable about the mayflies trout feed on in northern Wisconsin.

Nymph Habitat - the common water and stream bottom type the various nymphs prefer in a stream. The densest hatches are usually found where the nymphs ideal habitat is found. For example: Hexagenia limbata are burrowing nymphs that live in the silt and mucky areas of a stream and that is where the best hatches will occur during a Hexagenia emergence.
Most Common Hatch Time - this is generally what I have observed over the years, but this can vary a lot depending on water and air temperatures, cloud cover, etc.
Spinner Fall - the most common time of day or evening when a spinner fall will occur, there are always exceptions.
*** Sporadic indicates a mayfly that hatches off and on all during the day, not a dense hatch at one given time of day.

Notes:
(1) - indicates mayfly nymphs that burrow in sand, silt and muck. The densest hatches for these insects will occur in those stretches of the stream.

(2) - there are several mayflies species (Baetis, Plauditus, etc.) that all fall under Blue Wing Olives (BWO) and hatch at different times during the season. Some I see are too sparse to really get the trout's attention.

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