Abstract We examine and describe the embryonic development of 13 species from eight families of Dermaptera, i.e., all families excluding Karschiellidae, Hemimeridae, and Arixeniidae: Diplatys flavicollis (Diplatyidae), Cranopygia sp., Echinosoma sp., and Parapsalis infernalis (Pygidicranidae), Apachyus chartaceus (Apachyidae), Anisolabis maritima and Euborellia pallipes (Anisolabididae), Labidura riparia (Labiduridae), Forficula scudderi and Anechura harmandi (Forficulidae), Paralabella curvicauda (Spongiphoridae), and Proreus simulans and chelisochid gen. sp. (Chelisochidae). We also provide new findings on the reproductive biology of the Pygidicranidae and the postembryonic development of the Apachyidae. Based on information from the present and previous studies, we reconstruct the developmental and reproductive-biological groundplan for Dermaptera and discuss phylogenetic issues related to this order. We confirmed that Dermaptera possesses the embryological features (related to mode of embryonic formation and manner of blastokinesis) that are regarded as autapomorphies of Polyneoptera. Eudermaptera is characterized by the extraordinarily great length of the embryo which attains its maximum length in anatrepsis period, the positioning of its posterior end at the egg’s anterior ventral side, the type of egg tooth, and four larval instars. Anisolabididae, Labiduridae, and Eudermaptera share an elongation ratio of embryos in the anatrepsis period (ERE) of 160% or less and a larval instar number of five or less, whereas Protodermaptera is characterized by an ERE of 210% or more, a ratio of embryonic primordium relative to the egg’s longitudinal circumference (IL) of 40% or less, and a larval instar number of six or more. Notably, the ERE, IL, and larval instar number of Apachyidae are within the ranges observed in Protodermaptera.