I see these regularly in leaf-litter, but they have the habit of jumping away once disturbed. This one stayed-put and enabled me to get seven F5.6 shots to focus-stack (using Zerene Stacker).
The hind femora are very large (presumably this aids jumping) and makes me guess at flea beetle. Anyone confirm?
Canon 5D3 + MP-E 65mm (at 5x) + 1.4x Extender + 36mm extension tube + MT24-EX Flash. Magnification 8x. Beetle ~0.3.5mm. Cropped a bit.