Pipevine

There is a whole wall of this vine on my daily walk: the weathered fence is covered with these tiny striped pitchers hanging from thin stems. Aristolochia californica is also called Dutchman's Pipe and is the sole food source for the pipevine swallowtail butterfly, a strange arrangement that doesn't seem very efficient to me. I've looked for the caterpillars and butterflies for a year now, with no luck yet, but there are so many flowers there is bound to be a sighting sometime!