The present paper deals with the results of my investigations on the Tenebrionidae of the Leeward Group and the xerophilous regions of Venezuela and Colombia. I am much indebted to Dr P. Wagenaar Hummelinck for giving me the opportunity to study the material he collected during his trips to this area. Some other specimens used were collected by the present writer himself. Material for comparison has been obtained through the courtesy of several people, particularly the Director of the British Museum (N.H.), Mr H. Kulzer (Frey collection, Munich), and Prof. E. Tortonese (Museum of Zoology, Turin University), to all of whom I am deeply obliged. In particular I also wish to thank Prof. E. Gridelli, Director of the Natural History Museum, Trieste, to whom I am greatly indebted for his constant help and advice in my work, and to Prof. R. Malaroda, of the Institute of Geology, Padua University, for the useful criticism about my geological considerations. Not the last, I would express my gratitude to Dr E. MacC.Callan of the I.C.T.A. (Trinidad, B.W.I.) for the communication of material of that Institute. — The photographs were made by Dr P. Wagenaar Hummelinck, with the expert assistance of Mr H. van Kooten, at the Zoological Laboratory of the State University, Utrecht. The material has been deposited with the Zoological Museum of Amsterdam and the State Museum at Leyde. The material indicated as “Marcuzzi leg.” is included in author’s private collection, excepting some specimens which have been given to the Biological Department of the Caracas University, Venezuela.