Filariasis and Mosquitoes 181 



It was formerly supposed that when the infested mosquito punc- 

 tured the skin of man, the mature larvae were injected into the cir- 

 culation. The manner in which this occurred was not obvious, for 

 when the insect feeds it inserts only the stylets, the labium itself 

 remaining on the surface of the skin. Fulleborn has cleared up the 

 question by showing that at this time the filariae escape and, like 

 the hookworm, actively bore into the skin of their new host. 



Once entered, they migrate to the lymphatics and there quickly 

 become sexually mature. The full grown females measure 85-90 mm. 

 in length by .2 4-. 2 8 mm. in diameter, while the males are less than 



120. Filaria in the muscles and labium of Culex. After Blanchard. 



half this size, being about 40 mm. by .1 mm. Fecundation occurs 

 and the females will be found filled with eggs in various stages of 

 development, for they are normally viviparous. 



Filaria philippinensis is reported by Ashburn and Craig (1907) as 

 a common blood filaria in the Philippine Islands. As they describe 

 it, it differs from Filaria bancrofti primarily in that it does not exhibit 

 periodicity. Its development has been found to occur in Culex 

 quinquefasciatus, where it undergoes metamorphosis in about fourteen 

 or fifteen days. There is doubt as to the species being distinct from 

 bancrofti. 



Several other species occur in man and are thought to be trans- 

 ferred by various insects, among which have been mentioned Taba- 

 nidse and tsetse-flies, but there is no experimental proof in support 

 of such conjectures. 



