346 MEDICAL ENTOMOLOGY 



of the intestines of freshly killed goats has been used. This material can 

 be obtained from most Indian slaughter houses, and gives excellent 

 results. 



Another serious obstacle in these experiments is the fungus, Emfrusa 

 niuscae, which is very common in Musca nebnJo, and may be seen in 

 large numbers in the intestines of bazaar flies ; in this case they probably 

 become infected by ingesting the spores passed out by other flies. If the 

 dung becomes infected with this fungus the flies fail to hatch out of the 

 puparia. 



Musca nebulo may be kept alive for as long as four weeks in one of the 

 large cages mentioned above if certain precautions are taken. The floor 

 of the cage should be kept clean, and this is best done by wiping it daily 

 with a weak solution of carbolic acid. All dead flies should be removed, 

 and the food should never be allowed to remain in the cage long enough 

 for it to decompose or ferment. 



The great advantage of using bred flies is that they can be infected 

 either with bacteria or protozoa at any time, and the complete life history 

 of such a parasite as Herpetoinouas mnscae doinesticae can be worked 

 out. In gauging the results of such experiments, however, it is important 

 to remember that they are highly artificial and are carried out under 

 most favourable conditions. Such complications as temperature and the 

 effect of rapidly growing bacteria on the pathogenic ones should be 

 taken into account. 



It has already been pointed out that, in the case of experiments with 

 house flies, it is important to ascertain with certainty the species which is 



being dealt with and not to be contented with merely 

 House Flies which , , u , ., ,, , a T , i ' 



stating that it is the common house fly. It is also 

 may be mistaken for 



Musca very necessary to be quite sure that the same fly is 



used throughout the experiments. The various species 

 of Musca belonging to Group I are extremely difficult to recognize, 

 and for this reason specimens should be pinned and mounted in the 

 store box with full details regarding their habits, seasonal preva- 

 lence, etc., so that they can be submitted to an expert later. It is 

 necessary, therefore, to mention the several other kinds of flies which 

 may be mistaken for Musca domestica and its allies. 



All house flies do not belong to the genus Musca for many other kinds 

 of Diptera are attracted by food, and in this way come under notice. 

 There ought to be no possibility of confusing the various blue bottles with 

 Mitsca, for they are quite characteristic. In European countries, however, 

 there are several smaller diptera which at times come into houses and 



