A study of the collection of Dermaptera in the Rijksmuseum van Natuurlijke Historie at Leiden has been made by the author during the years 1942 and 1943, but publication of the results had to be postponed for several years on account of various difficulties arising during and since the war. These investigations yielded some interesting results, including the descriptions of several new species. It is intended to publish these descriptions in the near future after a study of the literature of the group that has appeared since 1943. Of the subfamily Diplatyinae the material of the Leiden Museum contains specimens of two forms that proved to belong to hitherto undescribed species. Together with other representatives of this subfamily these specimens were sent to Dr. W. D. Hincks of the Manchester Museum, for comparison with the material that formed the basis for his nearly completed revision of the group. Of the two forms referred to above, one appeared to be conspecific with a species to be described by Dr. Hincks in the near future, the other is described in the present paper, in order that notes on this species may be incorporated into the revision of the group. Diplatys sumatranus nov. spec. 1 ♂, Air Njuruk, Dempu, Sumatra, 1400 m, VIII 1916, coll. E. Jacobson. The present specimen is small and slender, of the usual general appearance in this genus (see fig. 1). Colouration: the head and the prozona of the pronotum are castaneous; the same colour, though less dark generally, is shown by the median part of the metazona, the elytra, a band along the outer margins of the wing-scales, Fig. 1. Diplatys sumatranus nov. spec. af habitus of male, and end of abdomen in lateral