Hex Mayflies
Hexagenia limbata
The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
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As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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Isidro
Posts: 24
Posts: 24
Isidro on Mar 17, 2008March 17th, 2008, 9:34 pm EDT
Im' not hoping an ID, due to the "success" of the last post of European mayflies. I suppose that if t's almost impossible identify mayflies by photo at adult phases, much more difficult will be at nymphal phases. But, maybe someone know, at least, the family of this one. This nymph was caught at Ebro river, in Zaragoza, NE Spain. This river is great and deep, slow and highly contaminated, with lime. The nymph sizes about 15 mm (without cerci). Can be identified, at least, at family level?
Many thanks.
Many thanks.
Taxon on Mar 18, 2008March 18th, 2008, 1:12 am EDT
Isidro-
Your mayfly nymph appears to be a clinger of family Heptageniidae, perhaps of genus Ecdyonurus. Given a decent macro photo, identifying mayflies to family and genus is actually somewhat easier with nymphs than with the winged lifestages, as the gross features on the nymphal lifestage are much more distinctive.
Your mayfly nymph appears to be a clinger of family Heptageniidae, perhaps of genus Ecdyonurus. Given a decent macro photo, identifying mayflies to family and genus is actually somewhat easier with nymphs than with the winged lifestages, as the gross features on the nymphal lifestage are much more distinctive.
Isidro
Posts: 24
Posts: 24
Isidro on Mar 26, 2008March 26th, 2008, 2:34 am EDT
Many thanks Taxon! This is very surprising for me. I hoped that teh adults would be much more easily identified than nymphs. The picture is not good but my camera don't give more. Thanks again for de ID.
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