Looking at more pics of Sitochroa in some it has the black band behind the head as in one of your pics, also the black front legs, makes silky webbing and has similar spots. What I'm wondering is if the eggs were laid on your carrots in anticipation of there being flowers and seed heads (one reference says they eat flowers as well) because wild carrot aka Queen Anne's Lace is flowering around here right now. Insects do make mistakes and so maybe all they can do in this case is eat the leaves because that's all there is. Do you have any Queen Anne's Lace around there? If you do maybe you could look and see if they are on there too, or put yours on some QAL and see what they do. Hopefully though the U of MN will come up with an ID.
