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Marsh Fly - Sepedon

Marsh Fly - Sepedon
Amherst, Massachusetts, USA
October 25, 2004
Shot in my backyard. I am guessing as to the family based on photos with anatomical similarites at Cedar Creek's site, so any input would be great.

That said, this was a really neat fly. As it perched on the grass it swayed (in a mantid-like fashion) as it warily watched the camera lens get closer and closer. I am glad it didn't fly off:)

Sepedon sp.
As Paul noted, this is a Sepedon species and the diagnostic characters are not visible in the image. However, this looks to me to be a blade of a sedge, which means that the fly is quite small. In your area, the most common small species of Sepedon is S. armipes, in which the male has highly modified hind femora, which the fly in this image lacks, whereas females have normal hind femora, like those shown here. If the blade is cattail, however, my guess would be Sepedon fuscipennis, a much larger species.

Not cattail
...if memory serves. Likely it was sedge of some sort.

Moved from Marsh Flies.

Marsh fly
This is a marsh fly or a snail-killing fly (family Sciomyzidae). There are too few details in the picture run it through the key. It is virtually impossible to get them all into one picture because some necessary hairs are minute, so this remark is not meant critisism on your picture. ;-)

My gut feeling is genus Sepedon because of the general build and the shape of the antennae. No certainty, though.


Thanks Paul,
Thanks for the verification Paul,

Also note, all of my images are GREATLY reduced to the jpegs you see here on the site, so if there is a tell-tale detail you are looking for, let me know as I can always post detail shots:)

Thanks again,I glad we have a Fly-expert contributing :)

Pandora's box?
God knows what I am risking by replying in this way, but I will do it anyway.

Characters that would get me much further in the key are:

detail of the thorax just above the humerus (shoulder) to see whether there is a strong bristle ther or not

detail of the ocellar area (area between te eyes where the ocelli are placed) to see if the ocellar bristle are developed

the side of the thorax just under the wing to see if minute bristle are present

the dorsal margin along the eyes to see whether large setae are placed there

the dorsal part of the thorax to see the development of acrostichal and dorsocentral bristles

the mid femur to see whether anterior bristles are developed or not

You see, I am not greedy, only needful ;-)
Moreover, parts may be out of focus and the details there not visible at all.


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