Sharing Caterpillars

[Sunsol]

I live in California and have grown fennel next to the sidewalk for years.
People collect caterpillars regularly. I feel rather ambivalent about this.
On the one hand I am glad that they know about anise swallowtails and enjoy
them, but on the other hand I think that the insects would be much better
off if these people took the  time to grow some butterfly plants themselves.

I am considering posting a sign asking the collectors to "give back" in some
way. I thought about asking them to pay, but that's not what I want. I want
to promote butterfly gardening and insect study. Has anybody got any ideas?

Sally