5s6 Sleeping Sickness 



they are so heavy that they can scarcely fly and drop off to the ground. Biting 

 is almost entirely confined to bright sunny weather. On dull or cloudy days the 

 flies remain in the brush. Exceptions are found among the few species that hve 

 in arid sections. Such may bite at night. Few of the flies fly far from their 

 native haunts where they seem to prefer to await the coming of their prey, rather 

 than to make excursions after it. Clouds of the flies often arise at the same time 

 and attack the animals in swarms. 



The flies are larviparous and do not lay eggs. Copulation of the sexes takes 

 place but once, the sperm being retained in a spermatotheca. The eggs are- 

 fertilized as they descend from the oviduct to the uterus where they hatch into a 

 larva on the fifth day. The larva grows rapidly, molts three times and attains 

 its full size by the tenth day, when it is born. The larva at the time of birth is 

 cylindrical in shape, consists of thirteen segments and measures 6-7 mm. in length. 

 It is nearly white but has a black head which is small and inconspicuous. The 

 larvae are usually deposited on the sand of the banks of streams or lakes, and at 

 once burrow into the ground to a depth of an inch or so. In a half hour or an 

 hour the larva changes to a pupa in which state it continues for about a month. 

 The imago or fly then emerges. The average duration of life of the imago fly is 

 about three months, during which time each female bears an average of ten new 

 larvae. 



Glossina palpalis is commonly infested by a flagellate called Crithidia grayi, 

 that seems in some way to pass from fly to fly, and to have nothing to do with the 

 bloods upon which it feeds. It is to be regarded as a parasite of the fly, and 

 should be known lest it be confused with the Trypanosoma of which the fly is 

 the vector. 



Table eor the Identification of the Common Tsetse Flies 



Large Species; body measuring more than 12 mm. in length. 



Pattern on thorax faint; four very distinct black spots . . G. longipennis. 

 Pattern on thorax sharp and distinct, no black spots. .G. fusca. 

 Small species; body in general measuring less than 12 mm. in length. 

 All five tarsal joints of the third pair of legs black. 

 Colors dark; antennas black; last two tarsal joints of 



the first pair of legs black G. palpalis. 



All of the tarsal joints of the first pair of legs yellow. G. bocagei. 

 Very small species; markings like those of G. morsi- 



tans on abdomen G. tachinoides. 



Colors dark; antennae yellow G. pallicera. 



Only the last two tarsal joints of the third pair of legs 

 black; all the others yellow. 

 The fifth tarsal joint of the first and second pairs of 



legs is yellow G. pallidipes. 



The last two joints of the tarsi of the first and second pairs of legs are black. 

 . The yellow band on the abdominal segments takes up 



one-third of the segment G. morsitans. 



The yellow band on the abdominal segments takes up 



one-sixth of the segment G. longipalpis. 



Full information and beautiful colored illustrations of the Tsetse flies can'be 

 found in E. E. Austin's "A Monograph of the Tsetse Flies," 1903 and iii his 

 "Handbook of the Tsetse Flies," igii. 



AMERICAN TRYPANOSOMIASIS 



SCHIZOTRYPANUM CrTJZI (ChAGAS) 



No sleeping sickness has thus far been found to occur upon either 

 of the American continents, though human trypanosomiasis in 

 another form has been observed in Brazil where it has been studied 

 by Chagas.* 



* "Archives fur schiffs u. tropen Hygiene," igog. Heft 4; abstract "Centralbl. 

 f. Bacteriologie, etc. Ref.," igog, xliv, 639; "Bull. delTnst. Pasteur," 1910, viii, 

 373- 



