18 Gerald F. Hilt: 



liberated 'm tlie vessel eoiitainiii<^ tlieiii. Tlie Stonioxys larvae pro- 

 duced only one fiy (January 7th), the result of examinati(ui of which 

 Avas negative. Between January 7th and 8th, 34 Musca doniestica 

 flies were examined, 21 of which, were positive and 13 negative for 

 Habronenia. The abdomen only of eacli of these Musca doniestica 

 flies were examined, the number of parasites found in eacli varying 

 from four to sixteen. Both species of fly larvae used^ in the experi- 

 ment were the progeny of eggs laid in tlie laboratory on sterilised 

 faeces bv naturallv bred flies. 



Exper'!me?ii A'o. 0. 



After a period of incubation in faeces, from 11 a.'m. on January 

 11th to 11 a.m. on January 16th, larvae of Musca doniestica and 

 Stomoxys calcitrans were liberated in the embryo-infected faeces. 

 These fly larvae hatched on January 7th, and were, therefore, nine 

 <lays old when exposed to infection. On January 30tli and the 

 two following days, 15 Musca doniestica flies were examined, all of 

 Avhicli were positive for Habronenia, the nuinber of parasites in 

 each varying from three to thirteen. On January 31st, and the 

 Ave days following, 49 Stomoxys flies were examined, all of which 

 Avere negative. 



€. To determine the frequency of larval Habronenia in Musca 

 doniestica, and their abundance and location in the 

 body of the intermediary host. 



(i) Free or caught flies. — During the period May-November, 

 1917, a recoid was kept of the number of flies (M. doniestica) 

 eaught in the stables, and examined for the presence of Habronema 

 larvae. It shows that 182 adult flies were examined, 14 of which 

 were infected with Habronema muscae (?), as follows: — Eight har- 

 boured one parasite each in the head, one harboured two parasites 

 in the head, one three in the head, four one parasite each in the 

 abdomen. 



(ii.) Although a similar record of laboratory bred flies has not 

 been kept, it has ])een noticed that in the great majority of cases 

 the abdomen only was infected, the proportion found in the head 

 being much smaller than in the abdonnen. This was piirticularly 

 fioticeable in heavily-infected flies. 



The occurrence of Habrcmema larvae in the distal portion of the 

 proboscis (haustellum) of Musca doniestica has not been observed by 

 the writer, although their occurrence in the proximal portion 



