272 KANSAS UNIVERSITY SCIENCE BULLETIN. 



through all of their modifications to the esophagus. Figure 14 

 will be useful for such a purpose. 



The lamella composing the frons passes into the clypeus (c) , 

 and then bends back on itself, forming the short, triangular 

 labrum {I). By bending a second time on itself, the longer, 

 similarly shaped epipharynx (e) is formed, with its under surface 

 well grooved to hold the stylets together. The lamella then dif- 

 ferentiates into the upper part of the pharyngeal canal (pc), 

 next into the upper part of the pharynx itself, and lastly into the 

 esophagus. The lower lamella first outlines the labium {lab^, 

 lah^, lab, and la) . It then passes back as the membraneous por- 

 tion (m) to the chitinized hypopharynx ( h) , which fuses with the 

 walls of the salivary canal {sc) . The walls of the cana' enlarge 

 into the injector {s.va). From the dorsal wall of the salivary 

 canal the lamella continues first as the lower portion of the 

 pharyngeal canal {pc) , next as the lower fold of the pharynx, 

 and lastly as the esophagus. 



The Hemiptera have always been known as sucking insects, 

 but the problem has been to find out how the food reached the 

 esophagus. From the descriptions of the parts, one must have 

 already noticed that two of the organs have the character of 

 pumps. Such is the case, the pharynx being an efficient suc- 

 tion-pump, while the salivary injector is a good force-pump. 

 Perhaps the action and relation of all the parts may best be 

 given by the imaginary feeding of some insect. 



The tip of the beak is fitted with a tuft of hairs, a fact which 

 is good evidence that the labium does not enter the body fur- 

 nishing the food. Papillae are present at the tip, and these 

 serve as organs of touch and taste. The proboscis is held 

 firmly against the bark, and, guided and supported by this en- 

 circling organ, the mandibles begin to bore, cut and saw their 

 way into the cortex of the plant. The serrations at the tips 

 of the mandibles (fig. 6, md) are especially fitted for this 

 class of work. Within the mandibles ply the maxillae, which 

 are able to pierce deeply with their sword-like points. That 

 this is the action of the stylets may be proved by the position 

 of the protractor and retractor muscles, which are arranged to 

 allow only such movements. 



As soon as this action is established the salivary injector 

 comes into play. The retractor muscles of the injector con- 



