|A baby jumper!|
He was tiny, so small that at first I thought he was just a crumb on the countertop. But then he turned to look at me.
|"Who are you, and are you good to eat?"|
Look at those eyes! In the first photo, you can see deep into their depths.
Jumping spiders have excellent vision; with those headlight eyes, they can see colour and distance, probably better than I do, although over a much more limited area. And then, there are all those other eyes, so useful! Every human parent should be asking for a few of these! There are four side-facing eyes, and a pair that looks straight backward. They don't see as well as the front pair, but they can detect motion and shadow, so that little Salty, here, saw me as soon as I moved in his direction.
|Diagram of visual fields of a jumping spider. By David Hill, via Wikipedia.|
|Salty's side and rear-view eyes.|
I found an article on Wired by Gwen Pearson, Spider Vision Made Clear, describing the movement and focusing of a jumping spider's eyes, and including this video, where the head is transparent, and the inner workings are visible. Watch:
YouTube video, By wmaddisn
The movement you’re seeing in the video is the front eye tubes and the muscles that adjust and point them. There’s a second lens at the end of the tube, and unlike the outer lens it’s flexible. Basically, jumping spiders have built themselves two little telescopes. By adjusting the angle and shape of the inner lens, the spiders can focus and zoom in on what they are looking at. (Gwen Pearson, Wired)
|Diagram of a Salticid eye, from the fabulously named paper, “‘Eight-legged cats’ and how they see”. Illustration: Fair Use; OA primary research|
Salty watched my camera lens for a while; that one big, black eye! What monster was looking through it? And then he decided it wasn't going to leap or do anything but shine lights in his eyes, and it wasn't edible, anyhow, so he turned his back on it and went about his business. Watching me behind him all the time, I'm sure.