Apple Maggots on underside of leaves on mackintosh and Gravensteins apple trees.
These images do appear to be Apple Maggot. I'll forward them to our entomologist for confirmation. Management efforts, especially protective sprays, for apple maggot also have the effect of controlling the other larval pest of apple, whose control is almost always required, codling moth. You will find information on apple maggot and it's control in the link below. Fee free to write back or to my email with further questions.