Unique Butterfly Detected in Minnesota Cabbage

Bill Hutchison, Eric Burkness, Patrick O’Rourke, Dept. of Entomology, University of Minnesota

During the past 4 weeks we have observed a unique butterfly (adults and larvae) in several cabbage research plots at Rosemount. The butterfly was identified this week by Dr. Susan Weller (Dept. of Entomology, Univ. of Minnesota) as the “Checkered white” (Pieris protodice). Although the adult, at first glance in the field, may resemble the closely related, and more common imported cabbageworm butterfly, this is a different species. The accompanying photographs illustrate the adult and late-instar larval stages; for comparison, we also provide comparisons with the imported cabbageworm (Pieris rapae). Thus far, larval infestations have not been high; maximum infestation level of checkered white larvae feeding on cabbage is approx. 2% (7/300 plants infested).

Checkered White	Imported Cabbage Worm
Checkered white adult	Imported cabbageworm adult
Checkered white adult - side view	ICW adult - side view
Checkered white larva	ICW larva

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Also note that the larval stage looks much different from another sporadic insect in cabbage, the zebra caterpillar (shown left) (Melanchra picta; Noctuidae).

The checkered white is NOT a new species to Minnesota, but is apparently vary sporadic in this part of its range. For example, during the past 10 years of extensive cabbage insect sampling at Rosemount, we have never observed this species. Further investigation via our Insect Museum, Dept. of Entomology, indicated that several specimens have been previously recorded, dating back to the 1920s. The last Checkered white specimens placed in our museum were collected in 1979.

The checkered white is known to occur from Mexico to southern Canada, and from New York to California. However, it appears to be more consistently common in the southern U.S. Interestingly, this species was also detected in Michigan for the first time this year, since at least 1995 (personal communication, Susan Weller). This appears to be a good year for many butterfly species.

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota, ctong@umn.edu
Production Editor: Suzanne Wold, Graduate Research Assistant, University of Minnesota, woldx018@umn.edu

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Last Revised August 2, 2001.
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