810 



AN INTRODUCTION TO ENTOMOLOGY 



Other mosqviito-borne diseases of man. — In tropical :ountries there 

 are, in addition to malaria and yellow fever, two other diseases of 

 man that have been found to be transmitted by mosquitoes ; these are 

 dengue and filariasis. The causative organism of dengue has not been 

 discovered ; but it is believed to be a protozoan of ultra -microscopic 

 size. Filariasis is due to the presence in the blood, the hnnphatics, 

 the mesentery, and subcutaneous connective tissue of nemotode 

 worms belonging to the family Filariidas, and which pass part of 

 their life-cycle in the bodies of mosquitoes. One of these parasites, 

 Filaria bancrofti, is the cause of the extraordinary deformities of 

 different parts of the human body known as elephantiasis. 



Mansdnia.—ln this genus "the larvse are peculiar in having the 

 air tube adapted for piercing the vascular roots of certain aquatic 

 plants, from which they get their supply of air. The eggs are de- 

 posited in rafts in swamps where suitable plants grow, and the young 

 larvae descend to the roots, never coming to the surface again." 

 (Dyar, '22). Mansonia pertHrhans is widely distributed in the United 

 States and Canada. Its larva lives attached to the roots of a species 

 of Carex growing in marshes or the edges of ponds. The winter is 

 passed as half-grown larva. 



Wyeomyia smlthii: — This species is remarkable on account of its 

 habits. "The larA'se live in the water in the leaves of pitcher plants 

 (Sarracenia piirptirea), passing the winter frozen up in the ice cores. 

 The eggs are laid on the still, dry, newly opened leaves and hatch 



when water collects in them" (Dyar 



Fig. 1026. — Mycelophila punctata. (Aftt 

 Johannsen.) 



'22). The adult can be distin- 

 guished from all other Culi- 

 cinse found north of Southern 

 Florida by the presence of a 

 tuft of sets on the metonotum. 



Family MYCETOPHILID^ 

 The Fungus-Gnats 



These 

 flies are of 

 medium or 

 sma 11 size 

 and more or 

 less mos- 

 quito-like in 

 form. They 

 are most 

 easily recog- 

 nized by the 

 length of the 

 cox£e (Fig. 

 1026). The 

 ncelli are 



