A few terms for the external parts of insects seem to better be rearranged.

Cranium

Insect head is a strongly sclerotized scull-like cranium, and it bears the mouth parts (Chapman, 2013). Snodgrass (1935) subdivided the cranium into frontoclypeal area, parietals, occiput, postocciput and subgenal areas. However, the clypeus and subgena are an undivided continuous plate to which all mouthparts (labrum, mandibles, maxillae and labium) are attached. And, then, it becomes a properly functioning mouth. In other words, without that long plate, it could never be a proper mouth. Therefore, the clypeus and subgena are better treated as the basic frame of the mouth, and termed as the “peristoma” as Snodgrass named firstly (Snodgrass, 1935). Then the cranium includes frons, parietals, occiput and postocciput only, and the mouth includes peristoma with the original mouthparts.

Following the above change, the term subgenal sulcus also better be changed to peristomal sulcus or cranio-stomal sulcus (Supplementary Fig. 1).

Ptilinal suture

Ptilinal sulcus is a transverse groove that crosses just above the antennal base and extends down laterally, in the form of an inverted U, towards the clypeus in adult schizophoran Diptera (Torre-Bueno, 1989). Though some workers treated it the same as the frontal suture in their books (Borror et al., 1976; Gillott, 1980; Imms, 1957; Torre-Bueno, 1989), it never be a suture because it does not fit any one of three categories (seam, sulcus, and ecdysial line in Matsuda (1965)) of Snodgrass (1960)’s definition. It is just an epidermal fold formed when the ptilinum is withdrawn after the adult emergence. Thus, it is better to follow the new term, ptilinal fissure (Colless and McAlpine, 1991).

Wing process

Snodgrass (1935) defined the wing process in his glossary as the wing support of the pleuron, or the lobe of the lateral margin of the alinotum supporting the axillary sclerite of the wing base. Process is described as the projection from the surface, margin or appendage (Gordh and Headrick, 2001). The wing processes are not a part of the wing but to which wings are attached. Therefore, the notal and pleural wing processes should be corrected into notal or pleural process, respectively (Chapman, 2013) (Supplementary Fig. 2).

Body plate

Body plates on upper sides are termed tergum and particularly that of thoracic segments are termed notum. However, the plates on lower sides are all termed sternum which is originally meaning breast or breastbone in Greek (Borror, 1960). Lawrence and Britton (1991) used a new term “Ventrite” for the abdominal lower plates of beetles which means under side or belly in Latin (Supplementary Fig. 3).

The term ventrite sounds meaning a subdivision, because the terms sternite and tergite is meaning subdivisions of sternum and tergum. So, it is better to suggest a new term “ventum” instead of ventrite.