Dimorphic jumping spider

Recently, when I finished a series of behavioral interactions with the Comanche harvester ant I study, this beautiful, small (about 5 mm), male jumping spider landed on my hand and distracted me from my work. I managed to shake him off my hand onto a plastic cup and got a few photos.

Jumping spiders are in the Family Salticidae, a name which derives from the Latin saltare, to jump or bounce, which suits these spiders perfectly. Unlike most spiders, the salticids (another name for jumping spiders) do not use webs to catch their prey; they pounce on them instead. In order to do this, also unlike most spiders, they have excellent, color vision. They have four color pigments (not three as we have). Their two large eyes (the AME or anterior median eyes) are the ones most important for their vision. These eyes look a bit like headlights.

One of the difficulties for spiders is that because they have an exoskeleton, the lens is hard and cannot be reshaped to focus their vision — the lens is part of the exoskeleton. However, the jumping spiders have overcome this problem by having moveable retinae. They have muscles which move the retinae up and down and all around — so they can focus and look around without moving their heads or rather their carapace. Quite amazing.

These spiders also use their vision in courtship. The males perform dances that show off their coloration to court the females. The females look for the right moves that show off the right color pattern — one way to identify species. To make this a bit difficult, the particular jumping spider which landed on me, Maevia inclemens, has males with two entirely different color patterns: a grey form and a dark form. Each color form has its own version of the courtship dance. The one I saw is the grey form. The males of the dark form are all black without other colors or patterns. The females look like the grey form in coloration. Now if you were a female salticid which would you choose?

Posted on August 7, 2013 11:06 PM by littleant