Small White-Pieris rapae
The Small White butterfly commonly called Small Cabbage White can be found in Europe, north Africa and Asia. It was accidentally introduced into Canada in 1860 from Europe and has since spread as far south as northwest Mexico.
In Chicago this white butterfly can be found just about everywhere from March to November. The caterpillar is often considered an agricultural pest because it feeds on edible plants like cabbage, radishes among other plants. In my garden it is most active during the middle of the day and for a long time I mistook this butterfly for a moth because it is so plain-looking.
I've not planted anything in my garden with the hopes of attracting this butterfly because it seems to be perfectly happy visiting the many weeds I let grow in my garden and I get some spill over from the many weeds that can be found in my neighborhood. I rarely see it visiting any of the perennials annuals that I've planted in the hopes of attracting insects to my urban garden. I guess there's no accounting for tastes. :)