ENTOMOLOGY

216 SANITARY ENTOMOLOGYevidence indicates that it can be carried by Glossina morsit0/n8 Westwood,G. fusca Walker, G. long..,ipennis Corti, G. pallidipes Austen, G.brevipalpis Newstead, G. tachittoides "Vestwood, as well as Stomoxyscalcitrans Linnaeu~, and the mosquitoes mentioned in another lecture.After the trypanosomes are ingested in the blood of the fly, multiplicationbegins, usually in the midgut (fig. 42). After the tenth or twelfth day,many long, slender trypanosomes are found which gradually move forwardinto the proventriculus. Such long, slender forms represent the limitof deyelopment in the lumen of the main gut. The proventriculus type,developed about the eighth to the eighteenth or twentieth day, is notinfective; it may occur in the crop, but is not to be found permanentlythere. Between the tenth and fifteenth days multinucleate forms oftrypanosomes are found, and may be styled multiple forms. Some ofthese latter may be degenerative. Long slender forms from the proventriculuspass forward into the hypopharynx. They then pass backalong the salivary ducts, about sixteen to thirty days after the fly'sfeed. In the salivary glands they become shorter and broader, attachthemselves to the surrounding structures and assume the crithidial facies.They remain attached to the wall and multiply. These crithidial stagesdifferentiate into the short, broad trypanosome forms, capable of swimmingfreely. These forms only are infective.After inoculation into the vertebrate these forms multiply by longitudinal'division.Repeated division occurs until the blood ~warms withparasites. They then disappear from the blood and become latent nonflagellatebodies in the intestinal organs. These latent bodies againbecome flagellate and enter the general circulation, and may be taken upby a bloodsucking fly. The above life cycle was worked out by MissRobertson as well as other workers and briefed by Fantham, Stephensand Theobald.Castellam.ella pecaudi (Laveran), cause of BALERI, a fatal equinetrypanosomiasis of Africa, is usually spread by Glossina longipalpisWiedemann and G. morsitans Westwood, but G. tachinoides Westwoodand exceptionally G. palpalis Robineau-Desvoidy may be infected.Stomoxys calcitrans Linnaeus and S. nigra Macquart are recorded aspossible carriers. The incubation period in G. longipalpis is 28 days.The trypanosomes multiply in the fly intestine up to 43 hours afteringestion in a modified form, called by Roubaud the "intestinal trypanosomeform." Under favorable conditions these multiply very rapidlyand in seven to nine days invade the whole of the intestine as far as thepharynx. These flies are not infective until the parasites have invadedthe proboscis and passed through the crithidial and leptomonad phases.These proboscis forms multiply and some reach the hypopharynx, where