Insects and Parasitic Diseases. 49 



In the second positive experiment (No. 10), 50% of the larvae 

 and flies examined were infected, the number of parasites in each 

 varying from one to ten. No embryos could be found in the pupae. 

 The abdomen only of adult flies was infected, and in one of these 

 eight of the total number of ten parasites were found in cysts. 



In the third positive experiment (No. 20), about 15.5% of the 

 flies (adults only) were infected with from one to sixteen parasites 

 each, all of which were located in the abdomen only. Of the total 

 number of parasites fi-om this culture about 50 per cent, were 

 encysted. 



The negative results obtained in Experiment No. 18 are very 

 strange in view of the fact that the only definite difference between 

 this and Experiment No. 17, which was distinctly positive, was in 

 the younger age (three days) of the fly larvae used in Experiment 

 No. 18, and in the fact that examination of the larvae, pupae, and 

 flies was commenced at three days instead of eleven days, though 

 in both cases it was continued up to fourteen days. The fact, how- 

 ever, that only a few living worm embryos were found in the culture 

 three days after the commencement of the experiment suggests that 

 either the infestation of the culture wa?, not sufficiently massive, or 

 that some unknown occurrence had killed off the majority of the 

 worm embrvos. 



C. To determine the viability of embryonic Habronema megas- 

 toma in faeces. 



Experiment No. 19, page 45, shows that embryonic H. megas- 

 toma may survive for a period of at least fifteen days in sterilized 

 faeces and remain infective to larvae of Musca domestica for a 

 period of at least seven days. Further, if one may judge by 

 analogy with H. microstoma the survival of H. megastoma larvae 

 for probably at least fifteen days in the sterile faeces suggests that 

 sucli infected faeces may remain infective for the full fifteen days. 

 At the end of this fifteen days, during which the embryos in this 

 culture Avere incubated at a: temperature of 22°C., 27°C., they were 

 found to be in the condition shown in Fig. 88, a and b. 



Reference to experiments Avith embryonic H. muscae and H. 

 microstoma shows that the periods of viability in these species was 

 not Iws than eight (the h)ngest period tested) and fifteen days 

 respectively. 



