﻿MICRO-ORGANISMS BY FLIES IN SAINT LUCIA. 



87 



same organism was grown. Needless to say that both the vessel andj the water 

 were sterilised, and control samples were kept in sterilised bottles. 



Fig. 4. — Limoslna punciipennis, Wd. X 16. 



It may therefore be concluded from the foregoing that flies are able to carry 

 pathogenic organisms from man to man, and from infected material to human 

 food and water, and infection may be conveyed which was acquired 24 hours pre- 

 viously ; but flies cannot carry organisms, which are pathogenic to man but 

 saprophytic to themselves, through their phases of development. 



Some natural enemies. 



The amount of flies and other insects destroyed by birds, frogs, lizards and 

 other creatures, cannot be gauged, and the only manner of arriving at some kind 

 of estimate is by examining the stomach contents of a large number of these 

 animals. As a result of thus investigating certain birds, frogs, and lizards, I have 

 come to the conclusion that flies are destroyed in far greater quantities by small 

 frogs and lizards than by birds in this island. 



Parasites which appear to harm flies are not numerous. Various acari are 

 found upon them 5 but the only one which seemed to destroy the life of the insect 

 was a small brown-coloured species which is very common upon the common 

 house fly (Musca domestica). Flies sometimes appear to be parasitized by fungi, 

 but this is a subject which requires much further research. 



In their larval and pupal stages their worst enemies are ants. If these find a 

 breeding ground they will carry off all the larvae and pupae, and I have lost the 

 entire number in several experiments in this way. Under more natural conditions 

 a number of factors prevent this action of ants from becoming very great. 



There are certain very small parasitic Hymenoptera of the family Chalcidi- 

 dae which are probably of some service in keeping down the numbers of some of 

 the flies here considered. These insects deposit their eggs in the body of freshly 



