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The data recorded in this report were derived from 4,796 feedings of Anopheles quadrimaculatus on monkeys infected with the M strain of Plasmodium cynomolgi, carried out between 1946 and 1958, from 262 and 193 feedings of A. freeborni on monkeys infected with the M and Ro strains between 1958 and 1969, and from 1,329 feedings of A. freeborni on monkeys infected with the B strain between 1958 and 1976. The yield of lots of A. quadrimaculatus acceptably infected with the M strain, 26%, was low, reflecting inability to relate appropriate time for bitings to either the gametocytemia or presence of exflagellating male gametocytes. This low productivity necessitated mass random feedings in order to service essential chemotherapeutic evaluations. A retrospective study of blood film-mosquito infectivity data acquired over a 7-year period suggested that there were close relationships between acquisition of well infected lots of A. quadrimaculatus and predominance of late ring stages of the M strain at time of feeding, and acquisition of negative lots of mosquitoes and predominance of early ring stages. On the basis of this observation, the predominance of late ring stages was used as the key to feedings of A. freeborni on monkeys infected with the M, B, or Ro strain. Coincidental with use of this selection procedure, there was a striking improvement in acquisition of lots of mosquitoes acceptably infected with the M strain. More importantly, routine use of this guideline made lots of A. freeborni well infected with the B or Ro strain accessible either continuously or at specifically targeted times.
* For present addresses see footnotes page 612 of this Supplement.
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