ENTOMOLOGY

106 SANITARY ENTOMOLOGYevery instance. Step by step, he proved that fly-larvO! talCe up bacteriafrom their food, and when breedinlg in flesh may take up disease germs aswell as non-pathogenic germs; that these germs may pass unalteredthrough the insects' intestines and out in their feces; that some of themmay remain for a long period in the intestinal canal, and some even.may multiply therein; that they may be taken up by the larva flInd persistthrough its metamorphosis until it arrives at the adult stage, andfor days thereafter, and may be carried by this adult and depositedwith its feces on food or excrement; and that these bacteria will also befound in the glutVnous sub~tances surroundV'-g the eggs when deposited,and thus contaminlate the substance in which the 'TIewly born larvae wi~lfeed; and of course be taken up by this seco'TId generation and possiblybe distributed farther by it.These facts were worked out by Cao in 1905 and 1906, and yetGraham-Smith credits Faichnie (who worked in India in 1909) with beingthe first one to suggest that bacteria ingested by the larva mightsurvive the pupal stage and be present in the intestine of the adult.Later, Bacot, and also Ledingham in 1911 and Graham-Smith in 191!,corroborated these claims that the bacteria could persist in the body'throughout the metamorphosis.Ledingham (1911), Nicholls (19Hl), and Graham..:Smith (191!)have shown that the fly larvre have great powers of destroying microorganismsdue to the fact that many of these organisms are not adaptedto the conditions prevailing in the interior of the larva and pupa, orperhaps more correctly due to the hostile action of bacteria which morenormally frequent the intestines of the larvre. These normal inhabitantsof the fly intestine are principally non-lactose fermenting organisms.Not only bacteria but also protozoa, such as the amoebae of dysentery,and the eggs of parasitic worms, may be taken up by the fly larvre oradults and deposited in the feces. Roubaud (1918) has brought outthe fact that multitudes of the amoebic dysentery germs taken up byadult flies and deposited in their feces die because of the rapid dryingof the feces, and he credits the fly with being a great agent in the destructionof multitudes of protozoa, while granting' the equally greatopportunity of the fly to contaminate food therewith .... Stiles in 1889 fed larvre of Musca domestica with female Ascan,lumbricoides, which they devoured, together with the eggs they contained.The larvae as well as the adult flies contained the eggs ofAscaris (Nuttall, 1899, p. 39). Nicoll (1911) has very thoroughly investigatedthe -relationships of flies to the possible carriage of eggs ofworms and demonstrated the ability of adult flies to ingest the eggs ofvarious species of 'vo~mJ, provided these are small enough, and to pass