Mayfly (genus Callibaetis)

2015-5-25 High Point SP, Sussex County, NJ
Roger Rohrbeck, of BG, 24 June, 2015, IDd this as a male subimago.
Because the quality of the picture precludes info beyond the genus, it was suggested (and I did) it be frassed.
The term "subimago" only applies to Mayflies.
It describes "the stage of development in an insect in which the insect is winged and capable of flight but not yet sexually mature. Occurs only in Mayflies (Ephemeroptera). With sexual maturity, the insect becomes an imago (adult) (...)"
the above from: http://bugguide.net/node/view/114117
Example images of subimagos are also at the above link.

Subimagos have tiny hairs on their wings that give the wing an opaque look. Their wings may be pale or a little darker, but won't be translucent. Imagos' wings are shiny and translucent. Their wings may have some patterning, but they will always be translucent.

Interesting write up on more of the life of the Mayfly:
http://www.west-fly-fishing.com/feature-article/9910/feature_90.php
Mayfly identification page:
http://www.flyfishingentomology.com/Adult%20Mayfly%20Identification.htm