IV PREFACE. 



Ortalides, Oscinides and Psilides are unnoticed ; but the Seasides 

 omitted are for the most part mere varieties. The Borborides 

 and the Hydromyzides are more complete, and are copied from 

 Mr. Haliday's excellent descriptions of the genera and species of 

 those tribes. The Geomyzides and the Phytomyzides are mostly 

 passed over ; but the (Estrida, the Hypocera, and the Eproboscidea 

 are rather fully detailed. Mr. Westwood has again prepared ten 

 plates for this volume, Mr. Haliday's state of health having 

 prevented his contributing the illustrations of the wing-veins of 

 Diptera. 



FRANCIS WALKER. 



December, 1853. 



