DIPTERA. 229 
fins. These nymphs also remain on the surface of the water, but in 
a different position from that of the larve, their respiratory organs 
being placed on the thorax; they consist of two tubular horns. It 
is in the water also that the perfect Insect is developed. Its exuviz 
form a sort of board or resting place, which keeps it from submer- 
sion. All these metamorphoses occur in the space of three or four 
weeks, and several generations are produced in the course of the 
year. 
In the excellent work of M. Meigen on the Diptera of Europe, the 
genus Culex of the preceding authors is divided into three. The 
species, in which the palpi of the males are longer than the probos- 
cis, and those of the females are very short, form that of 
CuLEx proper. 
C. pipiens, L.; De Geer, Insect., VI, xvil. Cinereous; abdo- 
men annulated with brown; wings immaculate(1). 
Those in which the palpi of the males are as long as the proboscis 
form another subgenus, 
ANOPHELES(2). 
Those in which they are very short in both sexes compose another, 
the 
fEpEs, Hoff.(3) 
M. Robineau Desvoidy, in his ‘* Essai sur la tribu des Cuculides,” 
has added three others. 
The species in which the palpi (labial, according to his theory) 
are shorter than the proboscis, and where the intermediate tibiz and 
tarsi are dilated and densely ciliated are designated collectively by 
the generic appellation of SanernxEs(4). Those, in which the pro- 
boscis is elongated and recurved at the end, and where the palpi, also 
short, have the first joint thickest, the other shortest, and the three 
(1) For the other species, see Meigen, Dipt., I, 1; Macq., Dipt. du nord de la 
Fr., Tipulaires, p. 153. 
(2) Ibid., I, 10; Macq., Ibid., 162. 
(3) Ibid., I, 13. 
(4) Mém. de la Soc. d’Hist. Nat. de Par., LIT, 411. 
