32 ENTOMOLOGY 



Hemiptera. The beak, or rostrum, in Hemiptera consists (Fig. 50) 

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

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



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 suck- 

 ing tube. Though primarily a sheath, 

 the labium bears at its extremity sen- 

 sory 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 to that 



FIG. 49. Hypopharynx of an ephe- 

 merid, Heptagenia. I, lingua; si, si, 

 superlinguae. After VAYSSIERE. 



FIG. 50. Mouth parts of a hemipteron, Benacus griseus. A, dorsal aspect; B, transverse 

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

 /, labrum; li, labium; m, mandible; mx, maxillae. 



of Lepidoptera and Diptera, as presently described, though it differs as 

 regards the smaller details of construction. 



