Insect and Spider Identification: Beetle ID, 1 by DMersh

DMersh wrote:
Any idea what the tiny black beetle is? Sorry can't get a better picture, they're incredibly small, less than a millimetre long, there's a few of them crawling around on the sand in a pot of cactus seedlings, I wondered if they're harmful to plants. They have a very striking pair of white dots, one either side on the main body of the insect but are so small I only noticed them through a strong magnifying glass.

Thanks

D Mersh