CULEX PIPIENS. 127 



thorax, and it rises with its head upwards to breathe through 

 them. As soon as the last change is at hand, the pupa 

 raises its thorax out of the water entirely, and slightly turns 

 up its tail, floating like a boat ; presently the skin bursts, 

 and the head of the enclosed perfect insect emerges, the 

 long antennae wave to and fro, and the frail bark rocks from 

 side to side in some peril, for the lightest breath of air would 

 overset it. Then one by one the legs are drawn forth and 

 stretched forward to some floating leaf or stick whereby to 

 steady itself ; slowly the rest of the body follows ; the wings, 

 hitherto pressed to its side, crumpled and damp, are dried 

 by the warm atmosphere, and the quick breathing of the 

 little Gnat sends a rush of air through the delicate veins ; 

 they are gently waved for a few seconds, then up and away 

 flies the rejoicing creature into its new and happy life. 



Such is the history of the pretty microscopic object on 

 the slide before us. 



Of its structure it is necessary to know that all the 

 Diptera are distinguished from other orders of insects by 

 having only two wings, and a pair of stout organs, called 

 halteres, which are supposed to represent the posterior 

 wings of the four- winged tribes, and respecting which ento- 

 mologists are much divided. They have been specially 

 noticed at page 147. The Diptera have mouths variously 

 constructed for their necessities. Their food is essentially 

 fluid ; the juices of plants or of insect bodies, and of decom- 

 posing matter, forming their nourishment; and therefore, 

 instead of the strong* horny mandibles of a Beetle, we find 

 in such flies as Tabanus a pair of lancet-like organs for 

 plunging into the skin of the animal whose blood it delights 

 in, and beneath these another pair, to which are attached 

 large palpi, exactly corresponding to the maxillae and max- 

 illary palpi of the Coleoptera ; a labium or lower lip, which 

 in all flower-haunting and honey-loving flies is very long 

 and beautiful, as in Khingia, Syrphus, Conops, and many of 

 the Muscida3; a labrum or horny borer prolonged in the 

 predacious flies, and very remarkable in the Empidae and 

 Asilidae, which have also a beautiful lower lip or labrum, 

 used first for steadying the lancets in their descent through 



