DIPTERA. 449 



FAMILY I. 



NEMOCERA. 



IN this family the antennae usually consist of from fourteen to sixteen 

 joints, and from six, or nine, to twelve, in the others. They are either 

 filiform or setaceous, frequently hairy, particularly in the males, and much 

 longer than the head. The body is elongated, the head small and rounded, 

 the eyes large, the proboscis salient, and either short and terminated by two 

 large lips, or prolonged into a siphon-like rostrum, with two exterior palpi 

 inserted at its base, usually filiform or setaceous, and composed of four or five 

 joints. The thorax is thick and elevated ; the wings are oblong ; the halteres 

 are entirely exposed and apparently unaccompanied with alulae. The abdomen 

 is elongated, and most commonly formed of nine annuli ; it terminates in a 

 point in the female, but is thicker at the end and furnished with hooks in the 

 males. The legs are very long and slender, and are frequently used by these 

 insects to 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. Some of the females 

 commit their ova to the water ; others deposit them in the earth or on 

 plants. 



The larvae, always elongated and resembling worms, have a squamous head, 

 always of the same shape, the mouth of which is furnished with parts analo- 

 gous to maxillae and lips. They always change their skin to become nymphs. 

 The latter, sometimes naked, and sometimes enclosed in cocoons constructed 

 by the larvae, approximate in their figure to the perfect insect, present their 

 external organs, and complete their metamorphosis in the usual manner. 

 They have frequently, near the head or on the thorax, two organs of respira- 

 tion resembling tubes. This family is composed of the genera Culex and 

 Tipula of Linnaeus. 



Some, in which the antennae are always filiform, as long as the thorax, 

 densely pilose, and composed of fourteen joints, have a long, projecting filiform 

 proboscis, containing a piercing sucker consisting of five seta?. They consti- 

 tute the genus 



CULEX, Linnceus, 



Or the Mosquetoes, where the body and legs are elongated and hairy ; the 

 antennae 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 proboscis, and composed of five joints 

 in the males, shorter, and apparently with fewer articulations in the females. 

 The proboscis is composed of a membranous, cylindrical tube, terminated by 

 two lips forming a little button or inflation, and of a sucker consisting of five 



G G 



