Acknowledgments.-I wish to thank Capt. A. R. Higgins, Director, U. S. Naval Medical Research Unit No. 3, Cairo, Egypt, for the courtesies and fine cooperation extended to me during my stay in Egypt. Special acknowledgment is due Harry H. Hoogstraal, Head, Dept. of Medical Zoology at NAMRU-3, for his able and stimulating direction. Thanks are alsio extended to Abdel Aziz Salah, Sayed Metwally, Ibrahim Khetr, Makram Kaisar, and Soby Gaber for technical assistance. I am particularly indebted to the following authorities for the determinations of the various ectoparasite species, rodents, flora, and miscellaneous arthropods: Harry H. Hoogstraal (Ticks); C. F. W. Muesebebeck (Lice); Robert Traud (Fleas); H. L. Keegan (Mites); Kamal Wassif, Ibrahim Univ., Cairo, (Rodents); Mohammed Hassib, Ibrahim Univ., Cairo, (Flora); P. Wygodzinsky, Fundacion Miguel Lillo, Argentina, (Thysanura); Edward R. Ross (Embioptera); 0. L. Cartwright (Dermestidae, Histeridae, Nitidulidae); E. A. Chapin (Coccinellidae, Cucujidae, Staphylinidae); R. E. Warner (Curculionidae); Miss Luella N. Walkley (Lathridiidae); W. W. Wirth (Drosophilidae); M. R. Smith (Formicidae); Miss Kathryn N. Sommerman (Atropidae); C. W. Sabrosky (Muscidae, Sphaeroceridae); and H. W. Capps (Lepidoptera). Identifications made at the British Museum of Natural History were as follows: Tenebrionidae, Miss C. M. von Hayek and E. B. Britton; Ptinidae and Staphylinidae, R. D. Pope and E. B. Britton. My thanks are also due to Harold B. Jkrdan, Administrative Assistant, College of Medicine, Howard University, for his assistance in connection with dontractural and other problems pertaining to this project. Dr. H. C. Hanson, Dept. of Biology, Catholic University of America, reviewed this paper and gave valuable suggestions which were gratefully received.