Most companies that spray don't keep people informed about the side effects. The EPA does not do their own studies. Those are done by the chemical companies. Lately in the news, I've been hearing about drug companies hiding information, auto companies hiding information, oil companies hiding information, the chemical companies hide information, too. Butterflies are very sensitive to their environment.
I'd like to recommend that you talk with the city about what you are seeing. http://www.monarchwatch.org/waystations/download.html
There are downloads on the Monarch Waystation website. http://www.monarchwatch.org/waystations ... ochure.pdf
The promotional brochure is a good one. Read page 2, "Why We Are Concerned". This can be printed and handed out.