ENTOMOLOGY

70 SANITARY ENTOMOLOGYincrease to twice or more than twice their original thickness, developinginto what is known as the sausage stage of general occurrence in thedevelopment of Filaria larvre. Developing beyond this stage they increaserapidly in length, cast their skins at least once, and in one to two weeksafter infection of the mosquito, or longer, according to temperature andthe species of mosquito infected, they complete their larval developmentso 'far as the intermediate host is concerned, reaching a length finallyabout three to five times the length of the first-stage larvre and a thicknessabout three or four times the original thickness. They leave the muscles,enter the body cavity, and migrate into various locations, posterior portionsof the body, legs, palpi, but in greatest numbers into the labium.From the evidence afforded by the experiments of Noe (1900) withDirofilaria immitis and additional experiments by Bancroft (1901),Lebredo (1904-1905), Fiilleborn (1908), and others, it has been concludedby analogy in the case of Filaria bancrofti that when an infectedmosquito bites a human being the filaria larvre bore through a thin portionof the labium known as Dutton's membrane, and more rarely other thinportions of the proboscis, actively penetrate the skin of the individualattacked, and reach the lymphatic system where they complete theirdevelopment to maturity.Both anopheline and culicine mosquitoes can serve as intermediatehosts of Filaria bancrofti including the following species (see alsoChapter XVll) :A'lWpheline mosquitoesAlfWpheles (Myzomyia) rossi Giles." (Pyretophorus) costalis Loew." (Myzorhynchus) sinensis Wiedemann." " "peditamiatus Leicester." "barbirostris Van der Wulp.Culex pipiem Linnaeus"""Aedes argen,teua Poirret (Stegomyiaqalopus Meigen)Aedes gracilis Leicester (Stego-myia)Aedes scutellaris Walker (Culexalbopictus Skuse)M amonioides 'UlTl,iformis TheobaldM anaonioides a'T/lTl,ulipes Theobald8cutomyia albolineata TheobaldTaeniorhynchus domesticus Lei­quinquefaaciatus Say (fatigamWiedemann)gelidus Theobaldsitiem WiedemannCuliciM mosquitoes~ester