The author desires to express his sincerest thanks to the authorities of the Zoological and Geological Survey of India and of the Asiatic Society of Bengal for allowing him to consult the necessary literature in their respective libraries, and to the members of the Lac Association Committee and Mrs. D. Norris, the Director of the Institute, for their generous help. He is also much indebted to Mr. W. B. R. Laidlaw, the Entomologist, for going through the manuscript, and to the artist, Mr. E. Heber, for the illustrations accompanying the paper.