VI PREFACE. 



in the previous lists of British DIPTERA. It has not been 

 thought necessary to enumerate the genera which Macquart and 

 Desvoidy have formed as dismemberments of those of Meigen, 

 nor yet certain others, the representatives of which will be found 

 included in the greater genera from which they were taken, as 

 the collective index of generic names and synonyms will direct 

 the student to these, and the complete Systematic Index is re- 

 served for the Supplement. As the sheets up to the end of the 

 index to this volume have been printed off several months since, 

 it was not practicable to incorporate the first list of Errata. The 

 Addenda and Corrigenda, and the general observations, have 

 been kindly prepared by Mr. Haliday ; and Mr. Westwood has 

 supplied two supplementary plates of generic illustrations instead 

 of two drawn by Mr. Haliday, to illustrate the venation of the 

 wings and the nomenclature adopted for the veins and areolets, 

 which also will find a place in the Supplement. 



FRANCIS WALKER. 

 February > 1856. 



The reader is requested to bear in mind that the Analytic Tables, 

 whether of families, genera, or species, are intended to apply only to 

 the British species described in these volumes, and that a more ex- 

 tended application of them would be liable to lead into error in several 

 instances. The change of plan, adopted at the very conclusion of the 

 present volume, having caused the Errata to be dispersed in several 

 lists, it is recommended carefully to note all the corrections from these 

 in the text. 



A. H. H. 



