DAHLGREN, THE MALARIA MOSQUITO 



25 



LABRUM 



HYPOPHARYNX 



SUCKING TUBE 



SALIVARY CHANNEL 



MANDIBLE 



STYLETS 



larger teeth. These latter pairs of instruments enter the wound made 

 by the point of the labrum, and with their saw-like blades, serve to 

 brace the head while the "sucking-tube" is thrust forward. By a to- 

 and-fro motion which alternates with that of the piercing tube, they are 

 pushed into the tissues together with the tube, and their fine teeth 

 undoubtedly also serve to lacerate the tissues in the wound and to pro- 

 duce an increased flow of blood at the point of the sucking-tube. 



All these mouth-parts, viz. : the labrum, the hypopharynx, the mandi- 

 bles and the maxillae, form a very compact bundle which, when not in 

 action, is almost entirely contained in a groove on the upper surface of 

 the lower lip or " labium" (Fig. 19). This is attached below the base 

 of the other mouth-parts. It is equal to them in length, but much larger 

 than all the others taken together, and is flexible and forms a sheath 

 which serves for their protection. 

 Its outer surface is beset with scales. 

 Of the whole bundle of mouth-parts 

 only the labium and upper surface 

 of the labrum are ordinarily visible. 

 At the tip of the labium, two small 

 pointed movable flaps, or "labellae" 



are hinged (Figs. 18 and 

 Proboscis ... f . , 

 of Male -")' which protect the 



points of all the mos- 

 quito's delicate surgical instruments, 

 when these are not in use. The 

 separation of these Haps exposes the 

 points ready for instant action (Fig. 

 26). The female alone sucks blood. 



In the male the maxilla? are lacking, and the tip of the labrum is blunt 

 and unfit for piercing. 



The first, though somewhat erroneous, account of the mouth appara- 

 tus of the mosquito is contained in Swammerdam's " Bybel der Natuure" 

 (1668) published in Holland in 1738. In 1739, the French scientist 



Reaumur published a description of the mosquitoes' man- 



s- i • • tt- n • i i i tt ^ Manner of 



ner ot biting. His illustrations, here reproduced (rig. 20), stinging 



show well how the soft labrum is pushed away and Hexed 



in biting, and how only the labellre remain in contact with the stylets at 



the point of their entrance into the wound. 



LABIUM 

 (PROTECTIVE sheath) 



FIG- 



CROSS SECTION OF THE 

 PROBOSCIS. 



The mouth-parts, which are re- 

 presented in solid black, are those 

 which the insect actively employs in 

 stinging. Female. 



