i 5 o I. AHMAD 



(Philippine Islands and New Guinea) occupy a central position in the genus, around 

 which are the four main species groups : 



i. luzonensis (restricted to Philippine Islands) and tagalica extending from the 

 Philippine Islands to Sarawak, Halmahera Island, with two black dots behind the 

 ocelli and brownish black tips to hind femora. 



2. sakdapolrakae (Thailand, Java, and Sumatra), discoidalis (Thailand, New 

 Guinea, Australia, Solomon Islands and New Hebrides) and solomonensis (New 

 Guinea and Solomon Islands) with a large rostrum extending beyond second coxae 

 and the black line on the side of the head and prothorax lengthening in the order 

 given above (which also, perhaps coincidently, corresponds with successive pro- 

 gression of the ranges towards east). 



3. lepida (North and Central India, Bhutan, Burma and Thailand), pseudohpida 

 (South India, Ceylon and Malaya) and luzonica (Philippine Islands, Sarawak and 

 Vietnam) (Text-fig. 473) which are smaller than the other species and possess the 

 second right lateral conjunctival appendage, which is short in lepida, elongated in 

 pseudohpida and elongated and curved in luzonica ; these appear to form a group 

 of allopatric species, the range of lepida being north of that of pseudohpida and of 

 luzonica north east of that of lepida. 



4. chinensis, acuta and oratorius, the most widely distributed species of all in 

 the Oriental and Australian regions and major rice pests, show progressive reduction 

 of the lateral black line (extending from antenniferous tubercles up to the lateral 

 side of collar, sometimes like two dots in chinensis, represented by one dot at collar 

 in acuta and completely absent in oratorius) and parallel with this a trend for the apex 

 of the claspers to become united, for whereas they are truncated in chinensis, one 

 lobe is produced in acuta and finally in oratorius, this lobe is enlarged and acutely 

 pointed and the other lobe is lost. 



ACKNOWLEDGMENTS 



It is indeed a great pleasure for me to thank the following : Professor O. W. 

 Richards who granted me facilities in his department, Dr. T. R. E. Southwood, my 

 supervisor who suggested the problem, for his constant encouragement and valuable 

 criticisms. Dr. W. E. China whose suggestions, criticisms and comments helped 

 greatly. I am glad to acknowledge my indebtness to other members of the Imperial 

 College Field Station and the British Museum (N.H.), namely Messrs. R. G. Davies, 

 M. Luff, J. W. Siddorn, W. O. Steel and Dr. M. S. K. Ghauri, Messrs. R. J. Izzard 

 and J. A. Grant respectively, for kind help in various ways. 



I am also grateful to the authorities of the following museums and to the members 

 of their staff mentioned for the generous loan of or access to specimens. 



1. British Museum (Natural History), London. 



2. Hope Collections, Oxford University Museum (Professor Varley, Mr. I. 



Lansbury) . 



3. Australian Museum, Sydney, Australia (Dr. J. W. Evans). 



4. South Australian Museum, Adelaide, Australia (Dr. G. F. Gross). 



5. Carnegie Museum, Pennsylvania, U.S.A. (Dr. G. Wallace). 



