Ephemera sp. Mayfly Kim Conrad photo

By Steve B. Schweitzer

This hatch chart is representative of most common Midwestern United States hatches (Minnesota, Wisconsin, Illinois, Ohio, Michigan & Southern Ontario Canada).  For colder weather, adjust the chart 1-2 weeks out and for warmer weather, adjust the chart 1-2 weeks in advance.

The lighter colored bars () represent marginal periods to fish the emerger or dry fly pattern.  It's best to fish nymphs during this timeframe.

The darker colored bars () represent peak periods where surface action will be at its' finest.  Be sure to fish emergers and dry flies during this period.

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Name	Size	J		F		M		A		M		J		J		A		S		O		N		D
Ants Beetles Crickets Grasshoppers	12-18
Leeches	4-10
Sculpins	1/0-10
Freshwater shrimp (scuds)	12-20
Midge chironomids	16-28
Tiny Winter Black Stonefly	12-18
Baetis (transitional season hatches) baetis spp	18-20
Early Stonefly	4-14
Micro Caddis hydroptilitdae	18-22
Blue Quill P. adoptiva	16-20
Grannom Caddis Brachycentrus spp	14-16
Sulphers Ephemerella spp	14-16
Yellow Sally's Isoperia spp	10-12
Brown Stonefly Cultus decisus	10
Gray Drake Siphlonurus sp	10-12
March Brown (Gray Fox) S. vicarium	10-14
Slate Drakes Isonychia bicolor	10-12
Early Brown Stonefly	12-16
Dark Hendrickson Ephemerella subvaria	12-14
Mahogany Dun Paraleptaphlebia adoptiva	16-18
Large Black Stonefly	2-6
Dark Hendrickson Ephemerella subvaria	12-14
Black Caddis Chimarra spp	16-18
Slate Wing Mahogany paraleptophlebia adoptiva	16-18
Early BWO's (blue winged olives)	18-24
Green Rock Worm Caddis	10-18
Cranefly	10-14
Sulpher Dun Ephemerella dorothea	16-18
Brown Drakes Ephemera simulans	10-12
True Hendrikson Ephemerella invaria	14-16
Light Hendrickson Ephemerella rotunda	14-16
March Brown Stenonenum vicarium	10-12
Summer Stonefly Peridae, Perlodidae, Chloroperlidae	4-16
Speckled Sedge H. orealis	12-14
Hex Hexagenia limbata	4-8
Cinnamon Sedge Limnephilus spp	10-12
Mottled Sedge Neophylax spp	10-12
Yellow-Brown Stone Agnetina capitata	6-8