PREFACE -- The present volume concludes this work. In the four volumes are described 382 species of Tenthredinidæ, 9 of Cephidæ, 5 of Siricidæ, one of Oryssidæ, and 179 of Cynipidæ, in all 576 species. The Appendix brings up our information to date, more particularly as regards the nomenclature and biology of the groups. As will be seen, considerable alteration has been made in the definitions of the genera, their number, as compared with what Thomson and myself have adopted, being greatly increased. The only remark I make on this subject is that if exotic species are to be treated according to the same method a large number of genera or sub-genera will have to be created. The Bibliography I have endeavoured to make as complete as possible; but, owing to the difficulty of getting access to many foreign magazines and Transactions of Societies, I have no doubt that many papers have been omitted. In conclusion I have to thank my correspondents for their valuable assistance ; and more particularly as regards this volume I have to thank Prof. Gr. L. Mayr, Prof. J. W. H. Trail, the Rev. T. A. Marshall, M.A., Mr. G. 0. Bignell, Mr. J. E. Fletcher, and Dr. J. T. Oudemans for much help.Sale, Cheshire; March, 1893.