MECHANISM OF SUCTION IN SCHIZONEURA LANIGEEA. 



325 



two maxillary stylets -work smoothly along the internal walls of the hypo- 

 pharynx. As they lie along the proboscis-groove, they are held in position 

 at the extremity of the proboscis by the folding over of the walls of the 

 Groove, which thus forms a tube through which the stylets pass into the 

 plant. 



Text-fig. 2. 



m.e.p. 

 oe.s 



p.m. 

 m.d.p. 



Schematic longitudinal section through the head, showing relation of parts. X 160" 

 The stylets have not been shown, in order to avoid confusion. The working of these 

 structures will be readily understood from figs. 2 and 3. 



At the same time the large protractor muscles of the mandibles (md.pr.) 

 contract, and pull down the mandibular levers^ so that the mandibles are 

 also forced into the plant *. 



* From examination of some sections of plant tissues with the stylets in position {Aphis 

 rumicis on Chenoimdium album), the stylets were found to pass between the cortical cells 

 in a more or less irregular course to the vascular bundles. 



28* 



