X PREFACE 



figs. 2 and 3), the Congo floor- maggot fly and its maggot, tlie 

 screw-worm fly (PL XXI, figs, i, 2 and 3), the screw-worm, and 

 the tumbu fly (PI. XXII, figs, i and 2) and to Dr L. Nicholls 

 for specimens of Oscinis pallipes. 



To Mr Edwin Wilson my special thanks are due for all the 

 time and care he expended in producing extremely accurate 

 illustrations of all the specimens, some of them very minute, 

 submitted to him. These drawings are reproduced in Pis. I-IX, 

 XVII, XXI and XXII, and figs. 1-4, 8-1 1, 24, 25. 27, 31, 

 and 32. 



For permission to reproduce illustrations, which had pre- 

 viously appeared in other publications, and for the loan of the 

 original blocks, I am greatly indebted to the Controller of His 

 Majesty's Stationery Ofi^ce (Pis. XIV, XV, XVI, XVIII and 

 figs. 13-16), to the Editors of The Journal of Hygiene {Vis,. XII, 

 XIII and figs. 20, 21, 22), to the Editors oi Parasitology (figs. 28, 

 29, 30), to Professor R. Newstead (Pis. X, XI), to the Editors of 

 the Quarterly Journal of Microscopical Science (figs. 5, 6, 7, 17), 

 to Professor R. Hermes (fig. 12) and to Frederick A. Stokes 

 Company (fig. 18). 



Finally, I wish to acknowledge the very great assistance 

 derived from the publications of Dr Howard, Dr Hewitt, Professor 

 R. Newstead, and the Local Government Hoard. 



G. S. G.-S. 



Cambridge, 



August 191 3. 



