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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Lateral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Male Stenonema ithaca (Light Cahill) Mayfly Dun Pictures

Based on the identical size, shape, and relative proportions of different body parts, I'm pretty sure this dun is of the same species as two spinners I collected at about the same time. The color is dramatically different, but that's to be expected with many of these species in the transition from dun to spinner.

Ruler view of a Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York The smallest ruler marks are 1 mm.
Lateral view of a Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York
Dorsal view of a Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York
Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York
Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York
Ventral view of a Male Stenonema ithaca (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of the Delaware River in New York

This mayfly was collected from the West Branch of the Delaware River in New York on June 7th, 2007 and added to Troutnut.com by Troutnut on June 8th, 2007.

Discussions of this Dun

Cahills
12 replies
Posted by Dryfly on Jun 5, 2010
Last reply on Jun 11, 2010 by Wiflyfisher
Do Cahills ever come off in enough numbers for a rise to occur? Around here, they trickle off annoyingly, and never get much trout attention.I am wondering about this, cause I saw some spinners at a DQ last night. Are they ever real important?

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Male Stenonema ithaca (Light Cahill) Mayfly Dun Pictures

Collection details
Location: West Branch of the Delaware River, New York
Date: June 7th, 2007
Added to site: June 8th, 2007
Author: Troutnut
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