(164) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 405 



passing uninjured either as eggs or as young larvae into the 

 alimentary tract owing to insufficient mastication. Or the 

 larvae may have entered per rectum, the eggs having been 

 deposited when the patient was visiting one of the old-style 

 privies where these flies, especially H. canicularis and 

 H. scalar is, frequently abound. These last two species are 

 frequently the cause of this intestinal trouble, and it is most 

 probable that the larvae enter per rectum. 



Owing to the inability on the part of the observers to dis- 

 tinguish the different species of dipterous larvae we have 

 little information as to their occurrence in these cases. 

 Stephens (1905) records two cases. Two larvae were pro- 

 cured which were stated to have been passed per rectum ; 

 one was H. canicularis and the other is described as 

 M. corvina. The latter larva was stated to possess eight 

 lobes on the anterior spiracular processes which " distinguishes 

 these larvae from M. domestica, which has seven only." I 

 suspect this larva was M. domestica, which has six to eight 

 lobes on the anterior spiracular processes. Some years ago 

 a number of larvae which had been passed by a child were 

 sent to this laboratory, and I found that they were M . domes- 

 tica. In 1905 some eggs taken from the stool of a patient 

 suffering from diarrhoea were sent to me and on examination 

 they proved to be the eggs of C. erythrocephala. The 

 larvae of the small house-fly, H. canicularis, as I have 

 already mentioned, have occasionally been found in the stools 

 of patients. 



In certain cases the larvae may wander from the mouth or 

 alimentary tract and get into the nasal passages or other 

 ducts, in which cases complications may ensue and result in 

 the death of the patient. 



IX. LlTERATUEE. 



A few of the more important references included in the two previous 

 bibliographies are repeated here for the sake of convenience. 



1909. Ainsworth, R. B. " The House-fly as a Disease Carrier," ' Journ. 

 Roy. Army Med. Corps,' vol. xii, pp. 485-498. 



