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migration to the pharynx accompanied by a morphological change to 

 sessile paramastigotes; metamorphosis of a few paramastigotes to 

 short-slender, highly active proboscis forms; and a final anterior 

 migration to the mouthparts. 



Since few paramastigotes of L mexicana were observed in the 

 pharynx of Lu. diabol ica , and were not obvious in the cardia and 

 stomodeal valve, a "paramastigote" precursor is open to question, at 

 least in the parasite-host combination used in this study. It is 

 suggested that the broad promastigotes attached to the stomodeal valve 

 (haptomonads) may be the precursors of the proboscis forms, putting 

 the "base camp" at the valve rather than in the pharynx. This agrees 

 with a report by Adler and Theodor (1931) that proboscis forms of L 

 d_. infantum in P. pernisciosus first appeared in the thoracic midgut 

 (cardia). Furthermore, it appears that more than just a "few" of 

 these precursors metamorphose to short-slender, highly active forms, 

 since in some dissections they numbered in the thousands, and instead 

 of a directed movement from "base camp" (stomodeal valve) to "summit" 

 (proboscis), they moved randomly in all directions. This is 

 substantiated by their presence in all parts of the alimentary tract 

 in some old infections and suggests that the term "proboscis form" is 

 a misnomer. 



Leishmania braziliensis guyanensis (strain MH0M/SR/807CUMC 1) . 

 The small sample of flies infected with L b. guyanensis (strain 

 MH0M/SR/80/CUMC 1) was too small for any conclusions to be drawn about 

 the ability of Lu. diabol ica to harbor the parasite. The high 

 percentage of hindgut infections (Table 4-6) is consistent with 

 findings of Johnson and Hertig (1970) that all Panamanian strains of 



