Subject: hundreds of caterpillars
Geographic location of the bug: Summerville, Northeastern Oregon
Time: 03:42 PM EDT
Your letter to the bugman: We awoke to hundreds of these caterpillars on the hollyhocks and crawling in the yard.
How you want your letter signed: Bob
Knowing the plant upon which an insect is feeding is often a tremendous assistance in identification, so we quickly located this BugGuide image of a Painted Lady, Vanessa cardui, caterpillar on Hollyhocks, and it looks like your individual. The Painted Lady is one of the most wide ranging butterfly species on the planet and it is sometimes called the Cosmopolitan, but interestingly, in the 17 years we have maintained What’s That Bug?, we cannot locate a single other image in our nearly 27,000 unique postings (26,988 to be exact) of a Painted Lady Caterpillar, though the genus is well represented with caterpillar images of the American Lady, Virginia Lady and Red Admiral. Since the species is so wide ranging, the caterpillar must have a more varied diet than some very localized species that feed on a single plant or genus of plants. According to BugGuide: “Caterpillars feed primarily on Asteraceae and Malvaceae, especially Thistles, Burdock, and Hollyhocks. Many other plants are used occasionally, including Nettle, Alfalfa, Soy Bean, Beet, Borage, Plantain, etc.” Painted Ladies are prone to mass migrations some years, and it was selected as our Bug of the Month for March 2015.
thanks so much. they are feeding on the hollyhocks and then once on the ground they all seem to be crawling north. it is interesting! Bob