caterpillar on dill

[AChinLee]

Hi Laura,

Sure sounds like young Black Swallowail larvae.  As they get older, their
markings will change to a distinctive vertical striping of black with either
green or white, and yellow dots laterally along the sides and top of the larva.

Alan


Response to: 

Hello to everyone-  There are two, half-inch long caterpillars on one of
my dill plants.  They are dark with a distinct white saddle pattern. 
Are these young black swallowtails?  Thanks,  Laura