

ANATOMY AND PHYSIOLOGY 



39 



The suctorial, or haustellate, orders are Collembola (in part), 

 Thysanoptera (in part), Hemiptera, Parasita, Trichoptera (imper- 

 fectly), Lepidoptera, Diptera, Siphonaptera and Hymenoptera (which 

 have functional mandibles, however). 



Hemiptera. The beak, or rostrum, in Hemiptera consists (Fig. 52) 

 of a conspicuous, one- to four-segmented labium, which ensheathes hair- 

 like mandibles and maxillae and is covered above at its base by a short 



FIG. 52. Mouth parts of a hemipteron, Benacus griseus. A, dorsal aspect; B t trans- 

 verse section; C, extremity of mandible; D, transverse section of mandibles and maxillae 

 c, suction canal; I, labrum; li, labium; m, mandible; mx, maxillae. 



labrum. The mandibles and maxillae are sharply-pointed, piercing 

 organs and the former frequently bear retrorse barbs just behind the 

 tip; the two maxillae lock together to form a sucking tube with two 

 canals: an upper, suction canal and a lower, salivary canal. Though 

 primarily a sheath, the labium bears at its extremity sensory hairs, 

 which are doubtless used to test the food. This general description 

 applies to all Hemiptera except the parasitic forms, which present 

 special modifications. A pharyngeal pumping apparatus is present, 

 which is similar in its general plan t,o that of Lepidoptera and Diptera, 



