70 SANITARY ENTOMOLOGY 



increase to twice or more than twice their original thickness, developing 

 into what is known as the sausage stage of general occurrence in the 

 development of Filaria larvse. Developing beyond this stage they increase 

 rapidly in length, cast their skins at least once, and in one to two weeks 

 after infection of the mosquito, or longer, according to temperature and 

 the species of mosquito infected, they complete their larval development 

 so far as the intermediate host is concerned, reaching a length finally 

 about three to five times the length of the first-stage larvae and a thickness 

 about three or four times the original thickness. They leave the muscles, 

 enter the body cavity, and migrate into various locations, posterior por- 

 tions of the body, legs, palpi, but in greatest numbers into the labium. 

 From the evidence afforded by the experiments of Noe (1900) with 

 Diroflaria immitis and additional experiments by Bancroft (1901), 

 Lebredo (1904-1905), Fiilleborn (1908), and others, it has been con- 

 cluded by analogy in the case of Filaria bancrofti that when an infected 

 mosquito bites a human being the filaria larvje bore through a thin portion 

 of the labium known as Dutton's membrane, and more rarely other thin 

 portions of the proboscis, actively penetrate the skin of the individual 

 attacked, and reach the lymphatic system where they complete their 

 development to maturity. 



Both anopheline and culicine mosquitoes can serve as intermediate 

 hosts of Filaria bancrofti including the following species (see also 

 Chapter XVII) : 



Anopheline mosquitoes 



Anopheles (Myzomyia) rossi Giles. 



" (Pyretophorus) costalis Loew. 



" {Myzorhynchiis) sinensis Wiedemann. 



" " " peditceniatus Leicester. 



" " barbirostris Van der Wulp. 



Cidicine mosquitoes 



Culex pipiens Linnaeus Aedes argent eus Poirret {Stego- 



myia calopus Meigen) 

 " quirnqmefasciatus Say {fatir- Aedes gracilis Leicester (Stego- 

 gans Wiedemann) myia) 



Aedes scutellciris Walker (^Culex 

 " gelidus Theobald albopictus Skuse) 



" sitiens Wiedemann Mansonioides wniformis Theobald 



Mansonioides amwidipes Theobald 

 Scutomyia albolineata Theobald 

 Taeniorhynchus domesticus Lei- 

 cester 



