“Their caterpillars eat woolly alder aphids,” explained Cade, as we both crept closer to the Harvester butterfly with our cameras ready. “And the adults sip on the aphids’ honeydew.”

I felt a little twinge of dismay. Woolly alder aphids are one of my favorite creatures! In the fall they float around like little fairies covered in wispy strands of white wax. I’ve written about them before. Just like most aphids, woolly alder aphids suck plant juices from a host. The alder shrub harvests sunlight, water, and air; the aphids harvest the alder’s sap; and then ants (and, I just learned, Harvester butterfly adults) feed on sugary honeydew secreted by the aphids. In return, ants provide the aphids some protection from predators…predators like the Harvester butterfly’s caterpillars.