Parsley

I plant parsley in my garden for the swallowtail caterpillar. They seem to love it and I enjoy having them around. This is the first one I have seen this year. I am still only seeing a few butterflies, Not even one a day and my butterfly bush is in full bloom. Usually the garden is full of them. My milk weed is also blooming and I have yet to see one on it. I wonder if there is reason for concern or if it is just me?