Probably an almost adult male, and all of 3mm long, this Hentzia jumping spider (Hentzia mitrata) was virtually invisible except when it moved. (Fully adult males are not spotted, like this one, and have larger and furrier chelicerae. There is a theory that resembling a female while it’s a juvenile can help protect a young male from competition with other male spiders.)
Mitrata (Latin for “head dress”) refers to the “crown” of bright red hairs on the heads of the males. (I think it looks like a ninja turtle headband, don’t you?) The copper color of these spiders is actually uncommon for jumpers; most jumping spiders are dark brown or black.
Like most jumping spiders, H. mitrata hunts by wandering from place to place, looking for prey (they really like my husband’s car for this, for some reason — but there’s also evidence they hunt in the canopies of trees). They only build webs to molt in, or to lay their eggs.
Jumping spiders are one of the few beasties where you can tell when they’re looking straight at you. They can’t move their eyes, but they can move their retinas in order to track you. They’ll also follow you with their whole bodies to keep an eye on you as you photograph them.
The above individual is likely a juvenile male, who will molt one or two more times before coming into his adult coloration. For comparison, here’s a female crowned Hentzia jumping spider:
I’d drone on and on about this for hours, because I love these spiders, but this article from the Peckham Society is much more in-depth than I’ll ever be.