518 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 live 

 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 incon- 

 spicuous. 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 FOR THE IDENTIFICATION OF THE COMMON 

 TSETSE FLIES 



Large Species; body measuring more than 1 2 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 1 2 mm. in length. 

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



Colors dark; antennae 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. morsitans 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 



AMERICAN TRYPANOSOMIASIS 

 SCHIZOTRYPANUM CRUZI (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 furschiffsu. tropen Hygiene," 1909, Heft 4; abstract "Centralbl. 

 f. Bacteriologie etc. Ref.," 1909, XLIV, 639; "Bull. delTnst. Pasteur," 1910, vra, 

 373- 



