242 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



their apices. The protractor muscle arises from the loral mandibu- 

 lar plates, the retractor from the head capsule. 



Maxilla (figs. 7, 8, and 9). — The maxillary stylet and maxillary 

 plate constitute the maxilla. The stylets are long and are broad at 

 their bases, which are continued into the back of the head capsule. The 

 apex of a stylet is provided with interlocking hooks. The maxillary 

 lever may or may not be present. A tubular gland opens at the base 

 of each maxillary stylet as a rule. 



mdi..^ 



Figs. 7-9. 



7. Mandibular and maxillary stylets of Corixa. 



8. Mandibular and maxillary stylets of Anisops. 



9. Mandibular and maxillary stylets and the hypopharynx with muscles of 

 Agraptocorixa. 



Mode of feeding in Hemiptera. — The apical segment of the labium 

 is provided with a large number of fine sensory hairs. Inside this 

 very segment the labial plate supports the stylets from below when 

 the latter are moving into the wound. In addition to it, the rails and 

 grooves on the sides of the hypopharynx maintain a fixed direction 

 of the movement of all four stylets. Taking the stylets themselves 

 it can easily be seen that the two maxillary stylets are interlocked 

 and move together like the hypodermic needle of an injection syringe. 

 The mandibular stylets can move along the sides of the maxillary 

 stylets independently of each other. The procedure of the operation 

 of the stylets at present accepted is that which has been proposed by 

 Weber (cited by Snodgrass, 1944). According to this view the 

 mandibles appear to be the effective piercing organs, and they work 



