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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

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.

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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This topic is about the Mayfly Family Baetiscidae

The mayflies of this family are known mostly for their curious shapes, but they can create excellent spinner falls, too. Read about Baetisca, the only genus in this family, for details.

Example specimens

grayling mi

Posts: 1
Tnoetzel on Jan 14, 2009January 14th, 2009, 11:44 am EST
are these flies the flies we call batflies? They look like a size 12 may fly on the water but have a very stubby abreviated and robust body. They are becoming more and more a factor where I fish on the Au Sable River. Do these spinners retract thier tail section into the thorax?
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Jan 14, 2009January 14th, 2009, 5:15 pm EST

Can't say that I've ever before heard of them being referred to by a common name of Batflies. However, I suppose the the black wing color in combination with the scalloped trailing edge of their forewings do "slightly" resemble the wings of a bat.
Best regards,
Roger Rohrbeck
Troutnut's profile picture
Bellevue, WA

Posts: 2758
Troutnut on Jan 14, 2009January 14th, 2009, 7:26 pm EST
These are surely your batflies. I haven't seen that name before, but I'll add it to the common names for Baetisca on this site because it's a good one. They fit the description perfectly, and nothing else does.

Their tails aren't retracted into the thorax or abdomen. They just have an unusual shape.

It's very interesting to see that they're a factor on the Au Sable, too. It wouldn't surprise me, given their importance on the Brule, which is a similar system.

What do you know about fishing this hatch? I'd love to hear some stories of Michigan batflies.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Pleasant Gap, PA

Posts: 1197
Shawnny3 on Jan 15, 2009January 15th, 2009, 12:09 am EST
Bat is also a nice contraction of Baetisca. I suppose one could argue that it should be Baet, but that might lead to more posts about Latin pronunciations, and nobody needs that...

Lee Wulff eschewed the dainty bodies typical of the dry flies of his day and tied his Wulff patterns with really prominent bodies. He claimed that fish seemed to like the meatier profile, and it goes well proportionally with the general bushiness of the Wulff patterns. I wonder if this is a reason fish like the Baetisca hatches - lots of protein per inch.

Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Jan 27, 2009January 27th, 2009, 12:48 pm EST

I suppose one could argue that it should be Baet, but that might lead to more posts about Latin pronunciations, and nobody needs that...

Surely you jest. We all need it. It's just that no two "experts" seem to agree.
Best regards,
Roger Rohrbeck
Falsifly's profile picture
Hayward, WI.

Posts: 660
Falsifly on Jan 28, 2009January 28th, 2009, 1:26 am EST

Mutillidae: moo-TILL-li-dee


You say caley-BEE-tis; I say caley-BAY-tis.

You say moo-TILL-li-dee; I say moo-TILL-li-day.

caley-BEE-tis; caley-BAY-tis,

moo-TILL-li-dee; moo-TILL-li-day.

Let's call the whole thing off.


I do not know which way to say
moo-TILL-li-dee, moo-TILL-li-day.
But I will bet (for all who care)
that interest in this small affair
is idle fun and baited snare.

The fish we seek don't care a whit.
It will not change their minds one bit.
With all these words, we prove once more
what's in a name is naught for sure--
it's just a way of keeping score!

You’ve got to love that exchange
When asked what I just caught that monster on I showed him. He put on his magnifiers and said, "I can't believe they can see that."
Martinlf's profile picture
Palmyra PA

Posts: 3047
Martinlf on Jan 28, 2009January 28th, 2009, 11:05 am EST
Well, there's a good summary of the current scholarship on Latin pronunciation. Ave atque vale, Falsifly.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell

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