Although the three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts , they do not appear to be any more closely related to one another than they all are to insects , which have external mouthparts .
Though the three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts , they do not appear to be more closely related to one another than they all are to insects , which have external mouthparts .