Found near Hudson, WI
That is the larvae of a sawfly, which is a member of the bee and wasp order of insects. That larvae is the elm sawfly in a young stage. Most are light green and get to be about 2″ long. These are the biggest sawflies in North America (found all over North America).
Older larvae are light greenish-white with black dorsal stripe. While feeding, the larvae usually coil their rear end around a leaf or twig. At rest the larvae roll into a characteristic tight coil. The larvae spin tough, papery cocoons in litter. Pink coloration is not common, most larvae are green to yellow in color.
Adult has black wings, shiny thorax with white/yellow spot on the top and have orange antennae. They are about 3/4″ long. Females commonly have a yellow banded abdomen.
Larvae feed on the leaves of elm, maple, basswood, willow, or birch. Adults girdle twigs.
Larvae give off a smelly chemical if disturbed to keep from being eaten. This insect overwinters in cocoons, and pupate in spring. Adults emerge May to June.
The larvae can eat a lot of foliage, so could be a pest on small landscape trees, but they are not considered a major pest of trees.
This insect does not sting nor bite.