Members of a Canadian Forest Service field crew took this image this summer of a swallowtail larva, one of several seen in the area over a few days. Note that the yellow dots completely divide the black bar into several segments. When poked, the larva extruded horns that were orange-red. The plant species was not identified, but most caterpillars were found close to the ground in herbaceous vegetation along skidder roads within a spruce-fir forest.

This image was scanned from a colour print.

Edited to correct id.