490 



MITZMAIN. 



animal. The time elements of these are averaged per fly in each 

 experiment. 



The surra guinea pig 127 used to supply the infection in these 

 experiments was infected through subcutaneous inoculation of an 

 emulsion of house flies which showed a great number of trypano- 

 somes as the result of feeding on the abraded tail of a surra 

 monkey. This monkey died showing marked lesions of the 

 disease at necropsy. Guinea pig 127 was used when its blood 

 was positive for trypanosomes, for a great number of experiments 

 outlined in this paper.' The animal died on the sixty-fifth day 

 of the disease, at which time blood from the heart showed an 

 exceedingly rich infection. 



Table VI. — Mechanical transmission with interrupted feeding of Stomoxys 



on guinea pigs. 



No. of 

 ex- 

 peri- 

 ment. 



Surra 



guinea 



pig 



used. 



Condition of blood of 

 donor relative to trypa- 

 nosomes. 



No. of 



Num- 



Length of 



healthy- 



ber of 



time fed on 



guinea 



flies 



surra host 



pig 



ap- 



(average 



used. 



plied. 



per fly). 







Seconds. 



68 



30 



20 



87 



20 



45 



118 



15 



16 



115 



12 



15 



130 



12 



18 



126 



15 



20 



111 



21 



20 



116 



26 



80 



81 



8 



20 



95 



8 



15 



106 



6 



15 



Interval 

 between 

 feedings 

 (average 

 per fly). 



Time 



required to 



complete 



meal on 



healthy host 



(average per 



fly). 



127 

 127 

 127 

 127 

 127 

 127 

 127 

 127 

 127 

 127 

 127 



Numerous 

 Swarming 

 Moderate. 



do 



Numerous 



do-— 



Moderate. 

 Numerous 

 Moderate. 



do.... 



.-..do...- 



Seconds. 

 40 



120 

 52 

 45 

 45 

 25 

 30 



120 

 40 

 20 

 45 



Mins. sees. 

 3 3 

 2 



Negative results were obtained in all of these experiments. 



Fifteen to thirty seconds are consumed by the fly in inserting 

 the proboscis to the depth of the bulb of the labium and to 

 the stage of aspiring the blood. Much depends on the strength 

 and rigidity of the labium in this regard, for, in a hungry fly 

 newly emerged, as much as two minutes is sometimes required 

 before the proboscis is sufficiently embedded to start the blood 

 flow either by capillarity or suction. 



Ordinarily, under conditions of an experiment, if the inter- 

 ruption takes place after two minutes, renewed feeding on the 

 second host does not take place for twenty minutes or more; 

 on the other hand, some flies may become engorged in twenty 



