The Acerentomidae are a family of hexapods in the order Protura. Acerentomids are not tracheated, and instead use cuticular gas exchange. ==Genera== ...
(from the article `apterygote`) ...ProtentomidaeAbdominal appendages 2-segmented with up to 4 setae, 2 pairs with terminal vesicles.Family AcerentomidaeAbdominal appendages ...