182 THE PARASITIC NEMATODE : IIABRONEMA MUSCAE CARTER 



paper read by Taylor before the Montreal meeting of the American 

 Association for the Advancement of Science on " The House-fly as 

 a Carrier of Contagion." This observer, when dissecting a house- 

 fly, noticed a minute thread-worm emerging from the ruptured 

 proboscis measuring eight-hundredths of an inch in length. Inci- 

 dentally, the same investigator reported the results of feeding flies 

 on the spores of the red rusts of gi'asses (Tricholoma) and found 

 these ingested. Generali (1886) describes a nematode from the 

 common fly, which he calls Nematodum spec. It is highly 

 probable, as my friend Dr A. E. Shipley suggested to me, that 

 Generali's nematode and the F. muscae of Carter are identical. 

 Diesing (1861) created the genus Habronema for the Filaria 

 muscae of Carter, and his description is practically a translation of 

 Carter's original description. Piana (1896) describes a nematode 

 from the proboscis of M. domestica, which, in the occurrence of the 

 male and female genital organs in the same individual, he says, 

 resembles Carter's nematode. He finds that at certain seasons of 

 the year and in certain localities it is very rare, while at others it 

 may occur in 20-30 per cent, of the flies. The larva, after fixation, 

 measured 2'68 mm. in length and 0'08 mm. in breadth. It was 

 cylindrical and gently tapering off at the extremities, with the 

 mouth terminal. 



In many hundreds of flies which I dissected when making the 

 morphological studies which have been described in the earlier 

 chapters of this book, only two specimens of this nematode were 

 found, but as I did not seek it specially it is very possible that 

 specimens may have been unnoticed. The specimens which I found 

 measured 2 mm. in length and agi'eed entirely with the descriptions 

 of Habronema muscae (fig. 78). Both specimens were found in 

 the head between the optic ganglia and the cephalic air sacs. 



Recently, a very complete and unusually interesting study of 

 Habronema muscae (Carter) has been made by Ransom (1911, 

 1913). This author has cleared up the mystery which hitherto 

 surrounded the parentage of this nematode and has discovered 

 that the adult is a parasite of the horse, the house-fly acting as a 

 carrier of the larval form. The following account is taken from 

 Ransom's description of the occurrence, structure and life-history 

 of H. muscae. 



