BACTERIAL DISEASES 



£97 



The history is as follows: — 



The femalq^/. lutzi lays its eggs in water; these hatch and produce 

 the imago, which is then seized by the D. cyaniveniris (according 

 to Kudi), and some eight to eighteen long, pale, yellow eggs are glued 

 one after the other to the velvet surface of the gnat's first second lo 

 third abdominal segments. 



The eggs are quite ready to hatch, and Sambon says that seme 

 of them quickly become uncapped, and that the anterior part of the 

 . larva is protruding. The mosquito now goes off to get a meal of 

 warm vertebrate blood, and while it is so doing the larvae drop out 

 of their shells and enter the skin via the hole made by the mosquito. 

 This much is known, but we may well ask whether this happens 

 with any other insects. Sambon says that the common house-fiy 

 spreads the book-scorpion, Chermes modosus, in this way, and says 

 that he has seenPediculus capitis do the same thing. If this be so, 

 then the study of entomology, applied to man and animals, has still 

 much work in front of it. 



Restricting our attention to Dermatobia cyaniveniris, the chart 

 of its carriage is as follows:— 



Dermatobia Myiasis. 



Parasite, 



Intermediary 

 Hosts. 



Infection. 



Inter- 

 mediate 

 Host. 



Inter- 

 mediate 

 ' Reser- 

 voir. 



Trans- 

 mission. 



Defih i 

 tive 

 Stage. 



Larva of 

 D. cyani- 

 ventris. 



Janthinsoma 



hitzi. 

 Carries eggs. 

 Only female. 



Mosquito sucks 

 blood ; larva 

 enters wound. 



Penetra tive. 



Man. 



Warm- 

 blooded 

 verte- 

 brates. 



Larva 

 escapes 

 from 

 skin. 



Free 

 living. 



D. BACTERIAL DISEASES. 



The spores of bacteria enable them to spread from host to host 

 with a degree of protection during the^ passage, but non-sporing 

 forms will be benefited by the aid of a carrier, which not merely 

 affords protection, but also a means of dissemination. We will 

 divide the discussion into flies, fleas, and lice. 



I. FLIES. 



This ' intermediary host ' is often a non-blood-sucking fly of the 

 nature of the ' common house-fly,' which is a potential carrier of 

 disease, because it and its kind frequent decaying matter and 

 excreta for the purpose of laying the eggs, while both it and its 

 larvae are filth feeders. 



If it and its allies only fed upon filth, there would be but little 

 harm, but, unfortunately, they are attracted to many articles of 



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