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Small Mayfly - Ephemerella invaria - female

Small Mayfly - Ephemerella invaria - Female
Ottawa, Ontario, Canada
June 6, 2006
Size: 8 mm body
Quite a few of these small mayflies were attracted to my lights last night. Any ID help would be welcome. Many of the mayflies had extruded an orange ball of material from the abdomen. Any ideas on what this might be?


Images of this individual: tag all
Small Mayfly - Ephemerella invaria - female Small Mayfly - Ephemerella invaria

Moved from Stream Mayflies.

Not a heptageniid
This appears to be a female imago of Ephemerella that has lost a tail. The species is probably E. invaria (compare to photos here). These mayflies produce an "egg ball" that is carried on the end of the abdomen and dropped from the air--the reason egg-layers of this type are known as "bombers"--or it is released all at once upon contact with the water. In contrast, heptageniids are "dippers." They release eggs a few at a time as they repeatedly dip down onto the water's surface. Although it is not unusual to see photos of female heptageniid imagoes extruding eggs, I don't know of any that form a single egg ball that is released all at once.

Not a heptageniid
Thank you very much, Lloyd, - very interesting information.


Moved from Mayflies.

Mayfly ID

Your mayfly is a female imago in the process of extruding an egg mass from her abdomen in anticipation of flying just above the water's surface in (or near) riffles of a stream or river, and repeatedly dipping her abdomen in the water to dislodge the eggs.

As for her identity, I believe it to be Heptagenia pulla of family Heptageniidae.

Mayfly ID
Thank you, Roger. I thought they must be eggs.

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