i 7 6 



COMPARATIVE ANATOMY 



palp. (5) A lower lip or labium, which is really the second 

 pair of maxillae whose component parts are fused together in 

 the middle line. 



at 



mx. 



f ,a. 



Fig. 37. 



The upper figure is a side view of the head of a female of Anopheles inaculi- 

 pennis, with the mouth parts separated but in their relative positions to one 

 another, magnified about twenty times. The lower figure is a diagram- 

 matic representation of a transverse section through the middle of the 

 proboscis of a female of the same species showing the relative positions 

 of the mouth parts when at rest. At, antenna ; cl, clypeus ; e, eye; 

 hyx, the sword-shaped hypopharynx ; la, labium ; Lex, labrum+epi- 

 pharynx ; mei, mandibles ; mx, maxillae ; -mx.p, maxillary^ palps ; sal, 

 groove-shaped duct of the salivary gland running in the mid-rib of the 

 hypopharynx. (After Nuttall and Shipley.) 



The so-called proboscis of the mosquito is formed by the 

 modification and adaptation of these mouth organs. The 

 labium is converted into a long fleshy half-tube, whose 

 extremity is divided into two lobes. In section the labium 

 is crescentic, with the concavity of the crescent directed up- 

 wards. It serves as a sheath for the guidance and protection 

 of six piercing organs or stylets, formed by the modification 

 of the remaining mouth parts of a typical insect. Of these 

 stylets one, formed by the fusion of the labrum with an 



