512 MODERN CLASSIFICATION OF INSECTS. 
( fig. 124. 7.), which continue to move about with agility by means of 
the tail and two terminal swimming organs. In this state they are ac- 
tive, but unable to take any nourishment; they also suspend them- 
selves at the surface of the water, but in an opposite position to that to 
which they previously were accustomed; the organs of respiration 
being placed upon the thorax, and consisting of two tubular horns; the 
body is much curved, and terminated by two slender oval plates. 
Here also the insect undergoes its final transformation; the exuvize 
of the pupa serving as a raft, upon which it stations itself until its 
wings are extended. These transformations are effected in the 
course of three or four weeks, whence there are several generations 
in the course of the year. The larva of Anopheles bifurcatus (Culex 
claviger Fabr.), as described by Fischer (ut sup. Meigen, tom. vi- 
p- 242., and Macquart, Suites a B. tom. i. p. 32.), differs in some re- 
spects from that of Culex, having two greyish oval tumours behind 
the head, and two others, but smaller, near the tail; beneath the 
latter is a great number of long sete. 
Mr. Stephens has published a monograph upon the British Culi- 
cide in the Zool. Journal, vol. i. No. 4., and M. Robineau Des- 
voidy an essay upon the family in general, in the Mém. de la Soc. 
Hist. Nat. Paris, tom. iii. 
Although so exceedingly numerous in individuals, the number of 
species in this family is but few, six genera having only hitherto been 
characterised, three of which only have been noticed as British. 
The Culex ciliatus, forming Desvoidy’s genus Psorophora, is re- 
markable for possessing a small appendage at each side of the pro- 
thorax. 

The family Treutipz * comprises a very extensive series of insects 
greatly diversified in structure, corresponding with the Linnean genus 

* Bretiocr. Rerer. TO THE TIPULIDA IN GENERAL. 
Freis. Monograph. Tanypodum Suecie, 12mo. Lund. 1823. — Ditto, Beschr. 
ein. n. g. Hydrobeenus, in Vetensk. Acad. Handl. 1829, — Ditto, Observ. 
Entomol. (Simulium) 8vo. Stockh. 1824, and in Thon’s Entomol. Archiv. 
vol. ii. 
Verdat. Geschichte d. Simulien, in Naturwiss. anz. d. Allg. Schw. Gesellsch. 
1822, No. 9.; and in Thon’s Archiy. vol. ii. 
