Artificial Prey Construction
I constructed artificial P. troilus larvae by pressing white modeling clay (Van Aken Plastalina) into 3D-printed molds (see supplemental file “3D mold.zip”). The resulting unpainted prey are 4cm long, approximately the size of a 4th or 5th instar larva. Larvae are eyespotted at this point in development (Fig. 1a). To attach prey to host plants, I inserted a short loop of 26-gauge flexible craft wire into each clay caterpillar, leaving the two ends of the loop exposed from the ventral side. I applied three layers of acrylic airbrush paint (CREATEX tan, yellow-green, and dark green) to create the appearance of green countershading, which is an important aspect of visual defense for many swallowtail species (Rowland et al. 2007). Using yellow and black acrylic paint, I hand-painted eyespots on half of the prey (“eyespotted”, Fig. 1b), while leaving the rest blank (Fig. 1c). I preserved the paint with one coat of Krylon matte finish spray. Finally, I measured the reflectances of both real and artificialP. troilus caterpillars using an Ocean Optics Flame Miniature (FLAME-S-UV-VIS-ES) spectrometer with Ocean Optics PX-2 Pulsed Xenon light source, calibrated with a 99% Labsphere reflectance standard (see supplemental figure 2).