Now that warm temperatures are a reoccurring theme for the year, ants take advantage of this time before summer's heat limits their activity. Some are prepare reproductive brood, while others opt to move, divide, or expand the nest in other ways. All this is done while carefully foraging and maintaining boarders with species that directly oppose their goals.
Foraging is typically done on the ground. Providing more spring ephemerals allows for greater surface area for the ants to explore, and perhaps bring them closer to eye level.
Aphids provide actual hot spots for ant food. Occasionally their populations grow out of hand for the host plant but they rarely kill the host. Some would argue resulting diseases if present.
Beneficial insects such as lady bugs, and hover fly larva help keep aphids from getting out of hand.
Nylanderia flavipes is an imported species. Though not invasive it's something of a tramp often found in potted plants.