We don't have any actual land where we can grow vegetables, so we make do with box box planters on wheels which we cart around to the sunniest spots on our back deck. Tomatoes have historically done quite well in these planters, so we put them in again this year. While shooting photos of the bright yellow flowers, I noticed a spider who had made her home in one of the prime locations for insect activity.
She's a member of the family Theridiidae...I couldn't get a good shot of her abdomen, so I won't be able to get any more specific with her identification.
Leafhoppers in large numbers are known crop pests, weakening any plant by depriving it of its sap. They digest the sap, then excrete droplets of sugary water from their abdomen, much like aphids do (the drops you see on your windshield after parking under a tree is due to sapsucking insects such as these).