Araneus diadematus

The other day Mark looked down at the plants growing by our front door and discovered a clump of teeny, tiny, yellow spiders with little black dots on their abdomens. 

Then he discovered another clump. 

The succulent they were on had been covered in about a hundred tiny webs and they were working on colonizing a nearby fern.

The Child took one look, said, "Nope!" and retreated inside.  There was some good-natured teasing about bringing the clump inside, but Mark squashed that idea with conjecture about how ironic it would be if I turned out to be allergic to them after bringing them in.

I wondered if they were clumped together because they were cold, and tried breathing on them.  They spread out, but I think they really wanted to clump together because they didn't go very far. 

I did some quick research; I think they're Araneus diadematus (cross orbweaver) spiders, and once they get old enough, they'll go their separate ways and turn into much larger spiders.