Alfalfa Caterpillar or Clouded Sulfur

Scientific name: Colias eurytheme Boisduval
(Lepidoptera: Pieridae)

Facts: The larvae of this species is referred to as alfalfa caterpillar. The alfalfa caterpillar is a representative of a group of butterflies known as yellows or sulphurs. The alfalfa caterpillar has at least two color forms, one yellow and one nearly white. Intermediates between these colors also occur. Alfalfa caterpillars can become exceedingly numerous in alfalfa and are sometimes pests of that crop.
Click here to see image of caterpillar.

Photo credit (adult and larval forms): Nick Grishin