PBEFACE. 



The present volume concludes this work. In the 

 four volumes are described 382 species of Tenthre- 

 dinidse, 9 of Cephidse, 5 of Siricidse, one of Oryssidse, 

 and 179 of Cynipidse, 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. 



VOL. IV. 



