102 



all dead and degenerating. The measurements of some of 

 these longer forms were 151*5 lx, 318 /x, and 424 /x long respec- 

 tively. Unfortunately, the preparations were lost through an 

 accident before a more complete examination could be made. 



The subject was not pursued any further, for at the time 

 it was thought that it had little bearing on the matter under 

 investigation. 



Larvae of H. microstoma.- — Larvae obtained from the 

 head and proboscis of Stomoxys calcitrans were found to be 

 distinctly shorter than the larvae of the other two species. 

 They measured from 1*5 mm. to 2 mm. in length by 41 ix 

 to 58 fi wide. The larvae had the same general appearances 

 as those of the other two species. The pharynx was 43*3 li 

 long; the nerve ring was 110 jx from the anterior end of the 

 body, and the anterior portion of the oesophagus was 116*6 /x 

 long. The anus was open and situated 66*6 /x from the tip of 

 the tail, which was pointed, and possessed a small rounded tip 

 furnished with minute spines. On transverse section the 

 cuticle was found to be homogenous and smooth, lacking all 

 appearance of longitudinal ridges. 



Observations on the power of the larvae to leave the 

 proboscis of the fly gave the same results as those obtained in 

 the case of the other two species. 



The following observation made during the winter is of 

 interest. — Proboscides were removed at the bend just posterior 

 to the bulb. These were placed in saline solution in sealed 

 chambers. One set was left at room temperature, 20° C, for 

 one hour, and when examined no larvae had left the proboscis. 

 Another set was placed in the incubator at 37° C. for one 

 hour. When examined the saline solution contained many 

 extremely active larvae. The first set which had been left at 

 room temperature was then placed in the incubator at 37° C. 

 for one hour. On examination the saline solution was found 

 to contain extremely active larvae. The proboscides were 

 then examined, and only an occasional larvae was found to 

 have been unable to leave the proboscis. 



Experiments made to determine the power of the larvae 

 to penetrate filter paper gave negative results. 



Summary and Discussion of the Salient Observations. 



Habronema muscat was found to pass through its larval 

 stages in Musca domestica, but showed no development in 

 Stomoxys calcitrans. H. megastoma was found to possess a 

 similar Hfe-history. 



H . microstoma was found to pass through its larval stages 

 in S. calcitrans, and show sometimes an aberrant development 

 in M. domestica. 



