THE VICTORIAN NATURALIST. 



with yellow fever. In the life-history of the two former are 

 numerous differences in detail, Stegomyia being more closely 

 allied to Culex, of which genus it was until recently a 

 member. 



The ova of Culex are generally laid in concave boat-shaped 

 masses on artificial collections of water, while the elliptical ova 

 of Anopheles float in loose masses of 40 to 100 eggs, or isolated, 

 each on its side, in natural collections of still or slowly flowing 

 water. The larvae of each, with the large thorax, flexible abdo- 

 men, and rotatory head, are very active, those of Culex feeding 

 on animal matter, often at the bottom, and those of Anopheles 

 chiefly on vegetable matter near the surface. _ The former, 

 being slightly heavier than water, hangs vertically, with its 

 head downwards and its long respiratory tube on the last segment 

 but one of the abdomen just piercing the surface film of the 

 water, these being air-breathing larvae. Anopheles larvae, on 

 the other hand, have no respiratory tube, and lie horizontally 

 just below the surface of the water, with the respiratory opening 

 near the end of the abdomen touching the surface film. When 

 disturbed a Culex larva will sink instantly to the bottom, while 

 Anopheles will glide away near the surface, or descend by vigorous 

 jerks of the abdomen, rising to the surface within about 15 minutes. 

 The pupae of these two genera are very much alike, except that 

 Anopheles, the head of which is much more baggy, assumes a 

 curled position, with its short and broad funnel-shaped respiratory 

 tube at the surface of the water. In Culex the position of the 

 pupae is nearly perpendicular to the surface, and the respiratory 

 tube long and slender. In each case this tube leads into the 

 thorax, so that the pupa, unlike the larva, is supported head 

 uppermost. The adults of these two forms are readily distin- 

 guishable. Culex, with its unspotted wings, has in the female very 

 short palpi, one on each side of the proboscis, and in the male 

 long, feathery palpi. The large and bloodthirsty adult of Ano- 

 pheles has in most species spotted wings and long palpi in both 

 male and female, the antennae of the male in each case being large 

 and feathery. When at rest Culex stands with its body bent, though 

 more or less parallel with the surface on which it rests, while 

 Anopheles has its body in a straight line, and more or less per- 

 pendicular to the wall on which it rests. The adult male is 

 always vegetarian in habit, while the adult female may be vege- 

 tarian or sanguinary as circumstances permit, the blood of very 

 many animals serving in place of that of man. The mainten- 

 ance of species during dry or frosty weather is brought about by 

 the persistence of the adult female in the former case, and of the 

 adult female, or often larvae, in the latter case, hibernation being 

 a common occurence. Fish, frogs, dragon-flies, and water-beetles 

 help to keep down the superabundance of the larvae and pupse, 



