340 



INTRODUCTION TO ZOOLOGY 



also he does not usually sting and draw blood from a living 



prey as does his mate, but 

 lives a harmless life, sip- 

 ping the nectar of flowers. 

 Correlated with this 

 difiference in food and 

 habit, we find a difference 

 in the mouth-parts of the 

 sexes. In the female, 

 the lower lip or labium 

 is much elongated, and is 

 soft and deeply grooved, 

 forming a trough in which 

 lie five very sharply 

 pointed, almost thread- 

 like rods (Fig. 261). The 



Fig. 260.— The Common Grey Gnat [Culex 

 pipiens), in characteristic attitudes 

 ■when at rest. 



The male above, the female below. The actual 

 length of body is -^ of an inch. 



two finest of these correspond to the 

 mandibles (Fig. 261, mnd); the two 

 slightly coarser rods, which have ser- 

 rated tips, to the maxillae (Fig. 261, 

 mx), and the fifth unpaired rod to an 

 outgrowth of the roof of the mouth, 

 not found in other insects, and called 

 technically the " hypopharynx " (Fig. 

 261, hypo). The labial trough is 

 closed above by the upper lip or 

 labrum, which is also long and 

 slightly grooved, and thus forms 

 with the labium a flexible tube. 



The tip of the labium ends in two 

 little fleshy lobes which are pressed 

 firmly on to the skin of her victim, 

 as the gnat prepares to bite ; the 

 lancets are forced into the flesh, 

 being kept steady by the terminal 



rinA ^^^0: 



Fig. 261.— Head of a Female 

 Gnat, with the mouth-parts 

 artificially separated in 

 order to show them all. 



lab, Labium ; lahr, labrum ; ma;, 

 maxillae ; m?ic7, mandibles ; 

 hyfo, hypopharynx. 



