Hairy, green caterpillars

July 5, 2016 11:01 AM
Blog Post

Last week, my lab crew found a few different caterpillars feeding in our soybean plots at the ISU Northwest Research Farm. They were hesitant to identify it in the field, so they brought one to me for a confirmation. First, I noticed it had a green body and green head and four pairs of prolegs on the abdomen. It is common to see green caterpillars in soybean (e.g., green cloverworm, soybean looper), but most don’t have four pairs of prolegs like this specimen.

alfalfa caterpillar
Alfalfa caterpillar; black arrows indicate prolegs and blue arrows indicate thoracic legs.
Photo by Erin Hodgson.

Upon closer inspection, the body seemed velvety and covered with black hairs. Most caterpillars I see have a smooth body or have relatively few hairs. The final clue was the two, thick, white stripes along each side of the body. The lines had blobs of orange and pink. It had to be alfalfa caterpillar! Most of you are familiar with the adult of this species – a white or yellow butterfly.

alfalfa butterflyalfalfa butterfly

Two adult color forms of the alfalfa caterpillar.

Photos by Charles and John Bryson,


Erin Hodgson Professor

Dr. Erin Hodgson started working in the Department of Entomology, now the Department of Plant Pathology, Entomology, and Microbiology, at Iowa State University in 2009. She is a professor with extension and research responsibilities in corn and soybeans. She has a general background in integrated...