48 Experiments with certain diptera. 



Habronema spp. 

 The infection of M. fergusoni, M. vetustissima and M. 

 ierrce-regince by Habronema muscce and H. megastoma has 

 been fully dealt with in another paper. 



Agamospirura muscarum n. sp. 



(1) M. fergusoni. A few specimens of this fly were 

 found infected from time to time up till September, 1919. 

 From that time up till January 1920, when the work was 

 concluded, the percentage of infected specimens rose con- 

 siderably, while at the same time the percentage of 

 M. fergusoni infected with Habronema fell to almost nil. 

 Flies from all localities around Eidsvold toA^-nship showed 

 similarly high infection, whether collected along the river 

 or in dry scrub country. Out of 81 cases of infection, the 

 number of worms ranged from 1 to 12 with an average of 3. 



The head alone was infected . . . . . . . . 13 times 



The proboscis alone 



The head and proboscis together 



The thorax alone 



The abdomen alone 



The head (including proboscis) and abdomen 



The head (including proboscis) and thorax 



The thorax and abdomen . . 



The head (including proboscis), thorax and abdomen 



The small stages were found in rather thick yellowish 

 cysts among the viscera in the abdomen ; fully developed 

 worms were also seen still encysted, but this stage was more 

 commonly found free in abdomen, thorax or head. The 

 tendency of the mature larva appears to be to migrate 

 tlirough the thorax to the head and proboscis. In many 

 cases where fully developed worms were found in the head 

 or thorax an equal number of the large, rather characteristic 

 looking, empty cysts could be found in the abdomen. In 

 several instances similar cysts were noticed in the abdomen 

 bat no worms could be found in any part of the body of the 

 fly. It is almost certain that these flies were originally 

 infected, the worms having escaped (as Hab.onema has been 

 proved capable of doing) from the tip of the proboscis of 

 the fly, while the latter was feeding on a wet surface. 



M. vetustissima,. An infected specimen was first met 

 with in September, 1919. Of four cases of infection, the 



