PREFACE. THE present work gives a systematic and biological description of the species of the Hymenopterous Families Tenthredinidæ, Siricidæ, and Cynipidæ, known at present to inhabit Britain. So far as the two first families are concerned, this is not the first work on the British species; for in 1835, in the seventh volume of his ‘Illustrations of British Entomology,’ James Francis Stephens described the species known by him to inhabit these isles. Stephens' work is now obsolete, while since its publication until within the last decade the plant-feeding Hymenoptera have been altogether neglected. This is a somewhat curious circumstance, considering that they are the easiest of all Hymenoptera to name, that many of them possess elegant and beautiful forms, and many interesting peculiarities of structure, while their life histories can be worked out with comparative ease, and afford biological and physiological problems of the greatest interest for investigation. The Cynipidæ or gall-flies have been even more neglected, and only a few fragmentary papers have been published on the British species.
The published works or papers on the British species and the workers at the groups being so few, I cannot hope that the present Monograph is very complete as regards the actual number of British species ; while, as will be seen, the life-histories of very many of our commonest species are quite unknown. I cannot hope either that I have escaped the errors of omission and commission incidental to a work of this kind, dealing as it does with little studied and little known animals ; but such as it is, I hope, that at any rate it will increase the number of students of these neglected, but most interesting insects, and thus lead to an extension of our knowledge of the British species and their habits. The literature being thus so scanty, my indebtedness is the greater to those gentlemen who have rendered me assistance by lending me specimens or giving me information. In this respect my thanks are especially due to Professor Westwood, F.L.S., Professor J. W. H. Trail, F.L.S., Professor Gustav L. Mayr, of Vienna, the late Professor Zaddach, of Königsberg, the late Dr. S. 0. Snellen van Vollenhoven, of the Hague, Dr. David Sharp, of Thornhill, Dr. Buchanan White, F.L.S., of Perth, Messrs. R. McLachlan, F.R.S., J. E. Fletcher, John B. Bridgman, Joseph Chappell, Edward Saunders, F.L.S., E. A. Fitch, F.L.S., 0. W. Dale, James Hardy, J. J. King, Thomas Wilson, T. E. Billups, J. G. Marsh, C. G. Bignall, Richard McKay, the Rev. T. A. Marshall, E. A. Butler, Herr Brischke, of Dantzig, and the late Fredk. Smith, of the British Museum. To Mr. J. E. Fletcher, of Worcester, I am much obliged for the great trouble he has taken in procuring me larvæ for figuring ; Mr. W. F. Kirby, of the British Museum, has given me bibliographical information which I could not obtain here from the absence of libraries ; while I have to thank the Secretary of the Kay Society, the Rev. Professor Thomas Wiltshire, F.L.S., Professor Rupert Jones, F.R.S., and Mr. J. J. Weir, F.L.S., for revising the proofs.GLASGOW; July, 1882.