THE ANIMAL CARRIERS OF DISEASES 



annoyance of a person desiring a rest on a tropical afternoon. It 

 works all day, but rests at night in any place which is dark. It is 

 not known whether it has a particular preference for the spots on 

 which to defaecate, as fiy-specks are abundant. It is believed to 

 defaecate about fifty times in twenty-four hours. A number of 

 experiments have been performed to see how far Musca domestica 

 can fly, but they are not satisfactory. It is believed that a female 

 fly becomes sexually mature and deposits ova in ten days after 

 leaving the pupal case, that she lays four batches of eggs at intervals 

 of ten to fourteen days, and that then she dies, but these figures 

 must be received with great caution. Jephson believes that the 

 limit of life of an adult fly is three weeks, but a hibernating or 

 sestivating fly must live much longer. Indeed, a fly has been known 

 to live sixteen weeks. 



Enemies. — The enemies of the house-fly are numerous, and 

 include fungi [e.g., Empusa musm), protozoa (?), nematode worms 

 (?), mites [i.e., larvae of Trombidium muscarum Riley, T. muscce 

 Oudemans, the genus Pigmeophorus, nymphs of Tyroglyphus) , 

 spiders, pseudo-scorpions, centipedes, larvae of beetles, ants, wasps; 

 also members of Cynipidae, insects which produce galls on plants 

 {e.g., Figites anthomyiarum and F. scutellaris attack the maggots, 

 while Spalangia niger of the Pteronialidae lays its eggs in the pupae) ; 

 and Stenomalus muscarum is also a pupal parasite, as is Nasonia 

 brevicornis, Pachycrepoideus dubius, and Muscidifurax raptor. 

 Toads, lizards, and rats are expert fly-catchers. 



Pathogenicity. — It is a carrier of the bacilli of enteric fever, 

 dysentery, cholera, infantile diarrhoea, framboesia tropica, anthrax, 

 tuberculosis, ophthalmia, oriental sore, and parasitic worms {e.g., 

 Ascaris lumbricoides) . 



Galliphora Robineau-Desvoidy, 1830. 



These are the blow-flies or bluebottles, of which C. erythroce^phala Meigen is 

 the common species. 



Enteric Fevers. 



Organism. 



Infected 

 Host. 



Infected 

 Reservoir. 



Trans- 

 mission. 



Protective 

 Host. 



Infection. 



Bacillus 

 typhosus. 



Man. 



Man. 



Typhoid 

 carriers. 



Bacilli in 

 urine and 

 faeces. 



Inge stive. 



Flies. 



Bacilli on to 

 human food. 



Contaminative . 



2. FLEAS. 



These insects have been accused of spreading leprosy and tuber- 

 culosis, but only one bacterial disease of man has really been proved 

 to be carried by them, and this is the plague, 



