-212- 



with the invasion of the pharynx and proboscis, in several 

 combinations of parasite and fly (Ki 1 1 ick-Kendrick, 1979). 

 Nonetheless, there is no universally accepted opinion on the form of 

 Leishmania deposited in the skin by the infected fly. Adler and 

 Theodor (1931) described forms in the proboscis in late infections of 

 L. d_. infantum in P. perniciosus Newstead as very short flagellates 

 with flagella longer than the body. They considered these the end 

 point of the life cycle in the sand fly and felt that under natural 

 conditions they were the most likely to enter the vertebrate host. 

 Adler and Ber (1941) measured flagellates (L tropica) , presumed to be 

 proboscis forms, found in a smear of fluid seen emerging from the 

 mouthpart puncture immediately after a female P. papatasi had fed on a 

 human volunteer. They measured 6.5 urn to 13 pm in length without the 

 flagellum; the flagella were 13 to 24 urn long. These measurements are 

 somewhat longer than the dimensions of proboscis forms of L mexicana 

 found in Lu_. diabol ica and Lu_. shannoni . Ki 1 1 ick-Kendrick (1979) 

 concluded that since no other morphological form has been seen in the 

 proboscis in Leishmania- infected sand flies, the description of Adler 

 and Theodor (1931) must apply to all mammalian leishmanias. 



It is uncertain which parasites are the precursors of the short- 

 slender, highly active proboscis forms. Ki 1 1 ick-Kendrick (1979) said 

 that they originate from paramastigotes attached to the cuticular 

 lining of the pharynx. He likened the pharynx to the "base camp" and 

 the proboscis to the "summit." He then suggested a sequence of 

 parasite development as follows: multiplication in the midgut or 

 hindgut (depending on the species); migration forward and attachment 

 of promastigotes to the stomodeal valve; cessation of division and 



