S. dorsatus, I believe.
*EDIT: Since the taxon change of Sitticus dorsatus to Attinella dorsata, I have few observations IDed only to genus as Sitticus, which is now inactive. These are mostly juveniles or females from the same location. A majority of my A. dorsata observations were made at this location, and I have not observed other Sitticus (Attinella/Attulus) there. Because of the large population of A. dorsata at this location, and the absence (or my inability to locate) other similar species here, I’m updating my previous IDs to A. dorsata, rather than Attinella. However if you think they are actually something else, or disagree with my reasoning, please let me know! As always, I am open to new information. :)
same location, and possibly same spider as http://www.inaturalist.org/observations/6044863
Tons of flies on the surface of the Great Salt Lake.
California Gull chases brine-flies, the abundant food source(along with brine shrimp) which draws so many migrating birds to the Great Salt Lake in fall.
Thousands upon thousands of these flies along the causeway to Antelope Island. Wonderful source of food for the many birds that come here.
Personally, I think teenager shoes smell awful, but the brine flies do not share my opinion! @redston_1