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. Halida/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. Halida/s state of health having 

 prevented his contributing the illustrations of the wing-veins of 

 Diptera. 



FRANCIS WALKER. 



December, 1853. 



