xni, b. i Barber: The Transmission of Malaria 33 



earlier part of this paper, there is some evidence that type Giles 

 of Malaya may differ, biologically at least, from A. rossi Giles of 

 India. Certainly the local type is easily infected experiment- 

 ally, while the Indian type is reported to be rather refractory. 

 It is difficult to get satisfactory epidemiological evidence 

 in Malaya in regard to type Giles, since it is there commonly 

 associated with fuliginosus, aconitus, and other potential carriers. 

 In one or two instances I have found the larva of type Giles 

 in the same part of a lake in which maculatus and kawari 

 were found. The immediate vicinity of a certain extensive 

 breeding place of type Giles near Kuala Lumpur was not parti- 

 cularly malarious, but the people in the vicinity, chiefly Chinese, 

 were in the habit of protecting themselves by means of bed nets. 

 In another group of houses half a kilometer away and situated 

 near a breeding place of maculatus the people protected them- 

 selves in a similar way and were comparatively free from ma- 

 laria. In both cases the population was relatively stable, and 

 possibly the introduction of a susceptible and less well-protected 

 group of people into either place might be followed by an out- 

 break of malaria. Type Giles showed a marked avidity for blood 

 in feeding experiments, and it is known to frequent dwellings. 

 These characteristics, taken in connection with the experimental 

 evidence, would bring this type under suspicion. 



Anopheles umbrosus. — The evidence obtained in these experi- 

 ments, both in regard to the artificially and naturally infected 

 insects, would confirm Watson's conclusion that A. umbrosus is 

 an important carrier in Malaya. The susceptibility of this 

 species under experimental conditions is relatively low, but it 

 may breed in immense numbers, and evidence from laboratory 

 experiments as well as from the condition of adults caught in 

 nature indicates that it is a relatively long-lived species. No 

 exact experiments were made as to its power of flight, but 

 adults were often found in considerable numbers at some dis- 

 tance from breeding places, so that it is probable that umbrosus 

 is a strong flier. 



Anopheles aconitus. — Stanton and James have recorded natural 

 and artificial infection of this species. There were but few 

 numbers in my experimental series, but the percentage of infec- 

 tions was high, and sporozoites occurred in the salivary glands. 

 This species is often found in houses and readily takes blood. 

 It may be found at considerable distances from its breeding 

 places, and although a small mosquito is apparently capable of 

 long flight. The evidence goes far to incriminate this species. 



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