BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 83 



Experiment II. — On January I5th, 1920, about 300 

 house flies bred on infected material were placed in a cage 

 and the same routine followed as in Experiment I. 



On January 16th .. 11 ffofirowemo escaped 

 On January 17th .. 3 J?. mtisccB escaped 

 On January 19th . . I H. musccB escaped. 

 On January 20th . . S H. muscce, 1 H. megastoma escaped 



Total number of Habronema 24. 



Total number which escaped in the two experiments 75. 



These observations lead us to the opinion that when 

 the larvae have reached their final stage in the fly, they 

 naturally make their escape from the proboscis by rupturing 

 it when the fly alights around the horse's mouth, moist 

 with saliva. The worms are then readily transferred to 

 the stomach with the saliva and proceed with theu' develop- 

 ment. 



We are of opinion that the larvse will also be similarly 

 liberated when the fly comes into contact with a suitable 

 surface, e.g., the conjunctiva, where they may set up 

 habronemic conjunctivitis ; any abrasion or sore, where 

 they could cause a granuloma ; or the}^ may reinfect a 

 granuloma and such would afford an explanation of cases 

 referred to by Bull, where parasites of different ages were 

 found. 



The wound made by one fly, e.g., a biting fly, serves 

 as an attraction for other flies, especially Stomoxys 

 calcitrans, M. fergusoni and M. vetustissima (see Johnston 

 and Bancroft, 1919), and may become infected with 

 Habronema larvae. Of course, all which fail to reach the 

 mouth are doomed to destrucbion. 



It seems to us probable that in Australia the chief 

 transmitter of Habronema, whether H. muscce or 

 H. megastoma, is Musca vetustissima, whose habits are so 

 closely associated with cattle. This species has a very 

 wide range, embracing the whole continent, being not 

 onl}" the common '" bush fly," but one which invades 

 the towns and cities where it is commonly met with out 

 of doors (Johnston and Bancroft, 1919). Our observauions 

 show that it becomes readily and heavily infected with 

 Habronema when the opportunity occurs. The larger 

 species, M. fergusoni, is also, no doubt, a xevy important 



