VI PREFACE. 



The phenomenon of Parthenogenesis, now known to 

 be of common occurrence with Sawflies, is a subject 

 well worthy of extended study, and one which, if our 

 knowledge of it were sufficiently comprehensive, might 

 throw light on physiological problems of the highest 

 importance. 



My third volume will contain the remainder of the 

 Tenthredinidae, the Siricidge, and the introductory part 

 of the Cynipidae, including a discussion on the pheno- 

 mena relating to the structure and growth of galls in 

 general. The fourth (and concluding) volume will 

 deal with the systematic portion of the Cynipidse. 



I have again to thank my correspondents for their 

 kind assistance, and have also to express my indebted- 

 ness to the Rev. Prof. T. Wiltshire, M.A., F.L.S., 

 F.G.S., and Mr. R. McLachlan, F.R.S., for having 

 looked over the proofs. 



MANCHESTER; 



January, 1885. 



