100 



two or three days, provided that desiccation is prevented. 



Larvae in an earlier stage of development have at times 

 been found in the proboscis along with larvae in the final stage 

 of development. 



Failure to produce an infestation of flies occurred- in 

 exactly parallel circumstances as in the case of the experi- 

 ments with Habronema muscae. 



All attempts to obtain any development of embryos of 

 Habronema megastoma in Stomoxys calcitrans failed. 



Larvae of H. megastoma. — Larvae obtained from the 

 head and proboscis of flies were found to measure from 

 2 - 07 mm. to 2*5 mm. long by 60 /x to 66'6 ju, wide. The larvae 

 had the same general appearance as those of H . muscae, but 

 in a few specimens a circular ridge posterior to the lips was 

 observed. The pharynx was 60 /x long; the nerve ring 

 116*6 [l to 126' 6 /x from the anterior end of the body, and 

 the anterior portion of the oesophagus 80 \x to 90 ju, long. The 

 anus was open and situated from 80 /x to 90 /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 possess fine longitudinal ridges to the 

 number of 40 or 42, as near as could be determined. 



Observations on the power of the larvae to leave the 

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

 the case of H . muscae. 



Experiments made to determine the power of the larvae 

 to penetrate filter paper gave negative results. 



The Life-history of Habronema microstoma 

 (Schneider, 1866). 



The methods adopted at this investigation have already 

 been mentioned. The embryos were obtained from the gravid 

 female. Fermenting lawn clippings were used as a breeding 

 ground for Stomoxys calcitrans, and an emulsion of the 

 embryos in saline solution was added to this material. 



Embryos of H. microstoma, — The embryos when taken 

 from the gravid female are usually very active, and they 

 remain active for some days in normal saline solution. They 

 measure from 90"9 jx to 122*8 jtx in length, and are enclosed 

 in a thin shell or membrane. When placed in saline solution 

 and tap water, respectively, they behave in the same way as 

 those of H. muscae. 



The embryos may live for some days when passed out 

 naturally with the faeces of a horse. The faeces of a horse 

 were previously examined, and found to contain embryos of 

 H. microstoma. These faeces were kept for ten days, and 

 then Stomoxys calcitrans allowed to deposit its eggs on the 



