Systematic Position and Structure 5 



and palpifers have to do with piercing only. Suck- 

 ing and the injection of saliva are performed by 

 means of the labium and hypopharynx. The labium 

 lies above the hypopharynx and is usually pressed 

 against it. On the mid-ventral line of the labium is 

 a deep gutter, which, together with the salivary gut- 

 ter on the dorsal side of the hypopharynx, forms a 

 tube through which the blood is sucked. When the 

 insect makes an attack, the entire cluster of lancets 

 is inserted en masse, the galea, or sheath, being 

 shoved back in a bow. Immediately a drop of saliva 

 is injected by means of the salivary gutter, which 

 lies on the mid-dorsal line of the hypopharynx. The 

 fluid is secreted by salivary glands situated immedi- 

 ately back of the insertion of the neck in the thorax, 

 a set on each side. From each of these sets comes 

 a duct, the two joining and continuing as one to the 

 base of the hypopharynx. Here the duct opens into 

 the "salivary pump," which forces the saliva along 

 the gutter into the wound. The sets of glands con- 

 sist of three lobes each. The lateral lobes secrete 

 saliva, the central lobe was supposed by Macloskie 

 to secrete the poison, but Smith considers it a reser- 

 voir for the secretion produced by the lateral lobes. 

 As to the question of poison being actually produced 

 by any of the lobes, Miall does not consider it posi- 

 tively demonstrated. The action of the saliva, 

 according to Macloskie, appears to prevent the coag- 

 ulation of the proteids in the blood and thus facili- 

 tates the sucking process. If the insect is allowed to 

 take its fill, it will draw back the injected saliva and, 

 so far as the author's experience goes, there is then, 



