48 Gerald F. Hill 



Experiment No. 20. 



This culture was prepared on December 13th in the same manner 

 as the three preceding ones. Musca doniestica larvae (three days- 

 old) were fed upon the infected matter fi-om the time of its prepara- 

 tion (December l'3th) until they pupated, or were dissected. On 

 December 21st and five succeeding days a total of :^6 larvae, 15 

 pupae, and 33 adult flies Avere examined, of which number 13 flies, 

 only were found to be infected with from 1 to 16 lai-val parasites^- 

 each. About 50% of the larval parasites were encysted. 



Experiment No. 21. 



This culture was prepared on December 19tli in the same manner 

 as the preceding ones. On the same day the infected material was- 

 given as food to ''clean," two-days-old larvae of Stomoxys cal- 

 citrans, and on January 4th and 5th 55 adult flies resulted, and' 

 were examined, with negative results. 



Experiment No. 22. 



Embryos from thirty or more gravid H. megastoma were mixed' 

 with saline and sterile faeces on January 23rd, and incubated at 

 roum temperature until January 29th, on which date living 

 embryos were found in cultuie. T'ive-days-old larvae of Stomoxys 

 calcitrans were fed upon the infected matter on January 29th and 

 subsequent days, and on February 14th 27 of the resulting adult 

 flies were examined, none of which was infected. 



B. To determine the frequency of larval Habronema megastoma 

 in Musca domestica and their abundance and location 

 in the body of the host. 



(i.) Free or caught flies. — Larval H. megastoma have not been; 

 identified in naturally bred flies that have been caught. 



(ii.) Laboratory bred flies showed a lower percentage of infection 

 than with either H. muscae or H. mic'i-ostoma, as will be seen by 

 reference to Experiments No. 17, page 47, No. 19, page 47, and' 

 No. 20, page 48. 



In the first of these experiments (No. 17) about 35% of the flies 

 examined were infected ; the number of parasites found in each 

 Musca domestica fly varied from 1-8, the averasze being two. The- 

 head and thorax were the only regions of the body infected. 



