2 The Philippine Journal of Science . wis 



A good deal of work was done on varieties of A. rossi. The 

 large number and the wide distribution of these forms make 

 them of interest from the epidemiological point of view, and 

 the abundance and accessibility of material made them a favor- 

 able subject for the study of certain problems in infectivity with 

 malarial parasites. 



At the time when these experiments were begun, but one 

 variety of A. rossi had been reported from the Malay Peninsula, 

 namely, A. rossi var. indefinitus Ludl. In the earlier feeding 

 experiments most of the material was collected in brackish water 

 near Port Swettenham. Here the imagoes varied little, and 

 it was assumed, probably on good grounds, that all were var. 

 indefinitus. Later a quantity of material was collected from 

 fresh water, in particular from a certain group of fish ponds near 

 Kuala Lumpur. In this lot of material much variability was 

 observed in the breadth of the first black palpal band. There 

 was a continuous series of specimens varying from those exhibit- 

 ing no such band to those with a terminal black almost equal in 

 length to the terminal white. Some specimens with the broader 

 band together with the corresponding larval skin were submitted 

 to Doctor Stanton, who noted that larva and imago were similar 

 to specimens collected by him in Java. He subsequently sent 

 some of the Java specimens to the British Museum, where they 

 were identified as A. rossi Giles, on the basis of the larval char- 

 acters and of the broader black band. Dr. S. T. Darling had 

 previously noted wide variation in the larvae of A. rossi collected 

 near Kuala Lumpur. It seemed probable, then, that we had 

 to do with two types of A. rossi, namely, A. rossi var. indefinitus 

 and A. rossi Giles or a form* somewhat similar to it, and further 

 studies were undertaken regarding the characteristics of these 

 two types. For the sake of brevity in description the two Ma- 

 layan types will be referred to as "type indefinitus" and "type 

 Giles." 



In the course of comparative infection experiments carried out 

 with these two types and in connection with other observations, 

 over 6,500 larvae and many hundred adults were examined. 

 Some of the results of these observations are summarized as 

 follows : 



Larva. — The chief characteristics of the larva of the two types 

 correspond to the published descriptions of A. rossi var. in- 

 definitus and of A. rossi Giles, respectively. The principal dif- 



