Missouri Master Naturalists- Springfield Plateau Chapter

Saturday, May 23, 2020

Hammer-jawed Jumping Spider

Spider 5 mm or 1/5 of an inch
I found this little critter crawling on the patio floor and was able to scoop it into a bug box.  It measured just short of 5 mm and traveled around with a measured pace, able to walk up on the lid upside down.  When I tapped the box is swung down on a silk safety line....Bingo!  A spider.

Jumping spider eyes-  Nash Turley
I couldn't tell anything more about it until I got some better macro closeups.  The next morning I got it out into sunlight for a better portrait.  Here you can see the prominent forward facing pair of large eyes typical of a jumping spider.  Its palps are relatively large as are the front legs


Jim Eckert on Bugguide
I didn't have a lot of hope but I tried INaturalist and the first pick was a Hammer-jawed Jumping Spider, Zygoballus sp.  I wasn't impressed with the match of their pictures so I entered "Zygoballus" into Bugguide and found the pictures including the one to the right by Jim Eckert which said "Note the dark femurs on the first pair of legs."  BINGO!



You have to love a spider named a Hammer-jawed Jumping Spider!  Common Spiders of North America emphasizes the dark front leg femur as an identifying feature.  They are usually found in grasslands with small shrubs which describes our back yard which Barb had converted to all native species.

For those who haven't used INaturalist, it isn't perfect but then a Barb reminds me frequently, neither am I.  It is a good place to start if you haven't any idea what you have photographed.  It does require a good picture so cropping shots and color correction as needed is a good idea.