(Vermont) Found several clusters of these on underside of ornamental dogwood shrub today. They are not eating much and I like to encourage moths and butterflies. They are yellow underneath and black or brown? stripes on top (their backs?)Right now, noon on a rather hot, muggy day they are not eating..curled up with each other…resting?
This caterpillar is the larvae of the dogwood sawfly (Macremphytus tarsatus), which is in the wasp order(Hymentoptera) of insects.
When the larvae are small they are covered with a white waxy coating then as they mature you see the colors like yours. They feed on all the different dogwoods and can cause significant defoliation. The larvae overwinter as pupa in rotting wood.
The adults are wasp-like sawflies that emerge in late spring to early summer. They then lay eggs on the undersides of the leaves. There is one generation per year.
This sawfly is found in the eastern half of North America.
If your shrubs begin to be defoliated, for control if you only have a few you can hand pick and destroy the larva. They are controlled in nature by parasitic wasps. However, if damage to the plant foliage is to the point of defoliating the plant before the larvae size reaches 1″ long then horticultural oil or insecticidal soap may be applied.
This insect does not bite or sting.