Observation date: July 27, 2017
Submitted by: Tdyts716
Specimen type: Photograph
Observation notes: this caterpillar was hanging out about two feet up off ground on the siding near our front porch, about two feet away from any plants but , not sure what this caterpillar's host plant would be, we have - yellow yarrow, Vera Jameson sedum, cut leaf maple as shrub, lilac, diablo nine bark shrub, barbery shrub, carl forrester grass, daylilies, iris, lots and lots of russian sage (perovskia), lots of blanket flower, some penstemon, some culinary sage, two grape vines
neighbors have juvenile aspen, maybe cottonwood?, we have a juvenile ash tree also.
Status: Resident
Verified by: mikefisher
Verified date: October 28, 2017
Coordinator notes: At your location in Weld County, chances are this is the caterpillar of the Two-tailed Tiger Swallowtail, more commonly found out onto the prairie in northern Colorado than the Western Tiger Swallowtail which has been recorded in your county also. The two caterpillars are very similar. The Western likes higher altitude thus it is much more commonly found in the mountains. This caterpillar is looking for a site to pupate and likely overwinter until next year. The primary host plant for the Two-tailed in urban location are Green Ash Trees and since you have a juvenile of this tree, it is most likely that was where it was feeding. The Western Tiger Swallowtail does eat Aspen as you mention it is in your neighbors yard. The caterpillars of both turn from green to reddish maroon just before they pupate. Mike
