THE ANIMAL PARASITES OF MAN 



being on the surface ; whereas the larva of Culex hangs head downwards 

 perpendicularly in the water, the point of the syphon only touching the surface. 

 In about a fortnight the larva is fully grown and becomes a pupa. 

 The pupa (fig. 270), which carries out the most remarkable jerky movements, 

 remains in the water, but partakes of no food. In shape it somewhat 

 resembles a tadpole, that is to say, it consists of a bulky anterior portion 

 on the surface of which the head, with its appendages, is recognisable, and 

 a more slender segmented abdomen. Above, on the thorax, there are two 

 small open breathing tubes for the conveyance of air to the tracheal 

 system. After three or four days the perfect mosquito hatches out, 

 remains a short time on the surface of the water until its chitinous 

 integument is hardened, and then flies away.. 





FIG. 270. Pupa of Anopheles maculipennis, Meig. (enlarged). (After Grassi.) 



The females that are fertilised in the autumn hibernate in sheltered 

 spots in the open air, or in houses, cellars, under stairs, in stables, barns, 

 &c., and are the progenitors of the first generation of the following year. 



In accordance with the climate of a country, or the kind of weather 

 of a year, the conditions in regard to the manner of life and the dura- 

 tion of the development of the mosquito varies. At all events, the life- 

 history of the mosquito elucidates many points relating to malaria which 

 were hitherto not understood. 



[The length of the egg, larval and pupal, life varies so much that it is not 

 possible to give an account of any value here. Frequently the eggs may incu- 

 bate in two days, whilst I have had Stegomyia fasciata eggs from Cuba that 

 have hatched out under abnormal circumstances more than two months after 

 they were laid (" Mono. Culicid.," vol. iii., p. 6). Some larvae, as Anopheles 

 bifurcatus, live for months during the winter. Some mosquitoes therefore 

 hibernate as larvae. The larvae and pupae of the different genera present very 



