184 THE PARASITIC NEMATODE : HABRONKMA MUSCAE CARTER 



tode was found in 170 larvae of M. domestica; this specimen was 

 encysted. 



The adults of Hahronema muscae were found in the stomach 

 of the horse together with the last larval stage, which is the last 

 stage in the fly and the first in the horse. The adult male of 

 H, muscae varies in length from 8 to 14 mm., and from 250 to 

 300 /x in maximum width. The female varies in length from 13 

 to 22 mm., and in width in the region of the vulva from 250 to 

 400 /ti. The cuticle is faintly marked with transverse striations. 

 The head is armed with two lateral and four submedian papillae. 

 The tail of the male curves ventrally. The spicules are very dis- 

 similar; the left spicule is long and slender measuring about 25 mm. 

 in length, the right spicule is shorter and thicker measuring about 

 500 fjb in length. In the female the vulva is situated about one- 

 third of the length of the body from the anterior end. 



The eggs in the uterus of H. muscae measure about 40-50 /j, 

 long by 10-12 /a wide. The embryos pass out of the body of the 

 horse in the faeces. It has not been determined whether they 

 undergo further development before entering the larvae of 

 M. domestica or whether their entry is forcible or with the food ; 

 the latter method of entry seems the more probable. The earliest 

 definitely knowTi larval stage of H. muscae found in the fly oc- 

 curred in a pupa from a culture of horse faeces. This specimen 

 measured 450 ^ in length. Second stage larvae were found 

 enclosed in a cyst. The sixth larval stage, which is the final 

 larval stage, was found in both flies and horses ; the length varies 

 from 2"6 to 3"2 mm., and the width at the widest part from 55 to 

 70 ^i. The larval stage is reached about the time the flies emerge 

 from the pupal state. The infection of the horse probably takes 

 place by the swallowing of infected flies or of larvae which have 

 escaped from flies. As the proboscis of the fly is a common 

 location of the larval nematodes the escape of the larval nematodes 

 on to the moist surface of the horse's lips is not unlikely. 



Ransom points out that the presence of larval nematodes in 

 flies is of interest to entomologists and sanitarians alike, as it may 

 serve as a means of determining with some degree of accuracy 

 Avhat proportion of flies in a given locality find their breeding 

 place in horse manure. 



