216 SANITARY ENTOMOLOGY 



evidence indicates that it can be carried by Glossina morsitans West- 

 wood, G. fusca Walker, G. longjpennis Corti, G. pallidipes Austen, G. 

 brevipalpis Newstead, G. tachin'oidcs Westwood, as well as Stornoxys 

 calcitrans Linnaeus, and the mosquitoes mentioned in another lecture. 

 After the trypanosomes are ingested in the blood of the fly, multiplication 

 begins, usually in the midgut (fig. 42). After the tenth or twelfth day, 

 many long, slender trypanosomes are found which gradually move for- 

 ward into the provcntriculus. Such long, slender forms represent the limit 

 of development in the lumen of the main gut. The provcntriculus type, 

 developed about the eighth to the eighteenth or twentieth day, is not 

 infective ; it may occur in the crop, but is not to be found permanently 

 there. Between the tenth and fifteenth days multinucleate forms of 

 trypanosomes are found, and may be styled multiple forms. Some of 

 these latter may be degenerative. Long slender forms from the provcn- 

 triculus pass forward into the hypopharynx. They then pass back 

 along the salivary ducts, about sixteen to thirty days after the fly's 

 feed. In the salivary glands they become shorter and broader, attach 

 themselves to the surrounding structures and assume the crithidial facies. 

 They remain attached to the wall and multiply. These crithidial stages 

 diff'erentiate into the short, broad trypanosome forms, capable of swim- 

 ming freely. These forms only are infective. 



After inoculation into the vertebrate these forms multiply by longi- 

 tudinal division. Repeated division occurs until the blood swarms with 

 parasites. They then disappear from the blood and become latent non- 

 flagellate bodies in the intestinal organs. These latent bodies again 

 become flagellate and enter the general circulation, and may be taken up 

 by a bloodsucking fly. The above life cycle was worked out by Miss 

 Robertson as well as other workers and briefed by Fantham, Stephens 

 and Theobald. 



Castellanella pecaudi (Laveran), cause of BALERI, a fatal equine 

 trypanosomiasis of Africa, is usually spread b}^ Glossina longipalpis 

 Wiedemann and G. morsitans Westwood, but G. tachimoides Westwood 

 and exceptionally G. palpalis Robineau-Desvoidy may be infected. 

 Stomoxys calcitrans Linnaeus and S. nigra Macquart are recorded as 

 possible carriers. The incubation period in G. longipalpis is 23 days. 

 The trypanosomes multiply in the fly intestine up to 48 hours after 

 ingestion in a modified form, called by Roubaud the "intestinal try- 

 panosome form." Under favorable conditions these multiply very rapidly 

 and in seven to nine days invade the whole of the intestine as far as the 

 pharynx. These flies are not infective until the parasites have invaded 

 the proboscis and passed through the crithidial and leptomonad phases. 

 These proboscis forms multiply and some reach the hypopharynx, where 



