- DIPTERA. 227 
2 
balance themselves. . Several, particularly the smaller ones, 
collect in the air in numerous swarms, and as they flit about 
form a sort of dance. ‘They are found at almost every season 
of the year. In coitu they are united end to end and fre- 
quently fly in that position. Some of the females commit 
their ova to the water; others deposit them in the earth or 
on plants. 
The larvx, always elongated and resembling worms, have 
a squamous head, always of the same shape, the mouth of 
which is furnished with parts analogous to maxille and lips. 
They always change their skin to become nymphs. The 
latter, sometimes naked, and sometimes enclosed in cocoons 
constructed by the larve, approximate in their figure to the 
perfect Insect, present their external organs, and complete 
their metamorphosis in the usual manner. ‘They have fre- 
quently, near the head or on the thorax, two organs of respi- 
ration resembling tubes. This family is composed of the 
genera Culex and Tipula of Linneus. 
Some in which the antennz are always filiform, as long as 
the thorax, densely pilose, and composed of fourteen joints, 
have a long, projecting, filiform proboscis, containing a pierc- 
ing sucker consisting of five sete(1). They constitute the 
genus 
CuLex, Lin.—Culicides, Lat. 
Or the Mosquetoes, where the body and legs are elongated and hairy; 
the antenne densely pilose, the hairs forming tufts in the males; the 
eyes large and closely approximated or convergent at their posterior 
extremity; the palpi projecting, filiform, hairy, as long as the pro- 
boscis, and composed of five joints in the males, shorter and appa- 
(1) They have been well represented by Réaumur and Roffredi. The figure 
given by M. Robineau Desvoidy, in his Essai sur la tribu des Culicides—Mém. de 
la Soc. d’Hist. Nat., If, 390—conveys a wrong idea of the disposition of these 
sete. This writer has promulgated an opinion relative to the correspondence of 
these parts with their sheath, almost diametrically the reverse of that which is ge- 
nerally received. Had he reflected that two of these setz, in the Syrphi and other 
Diptera, are annexed to the palpi, he would not have taken them for mandibles, 
but considered them as analogous to jaws. 
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