LESSON 38.] 



NUTRITION IN INSECTS. 



135 



FIG. 221. 



FIG. 220. 



gizzard (&), and its four teeth, are seen just in advance of the com- 

 mencement of the stomach. The crop is opened to show the teeth. 



617. The mouth in the next order, Hemiptera, or the Tree bugs, 

 has undergone remarkable modification the whole of it is trans- 

 formed. In place of well-formed upper and under jaws, we have only 

 four delicate bristles ; and these are so fine and fragile, that when 

 not in use they require the protection of a sheath, which is specially 

 developed for their preservation. The mouth of these insects is dis- 

 tinguished by the possession of a jointed organ called the rostrum 

 (Fig. 221). This has from three to five joints. The organ itself 



is simply an altered form of the 

 lower lip, which in these insects 

 forms the sheath or protecting case 

 alluded to. 



The remainder of the apparatus 

 of this curiously formed mouth is 

 shown in Fig. 220. The upper 

 lip (a) is a long, slender, somewhat 

 triangular scale ; its office, however, 

 appears to be uncertain, the jaws 

 being confined in the rostrum. The 

 bristles representing the upper jaws 

 are seen at b, and the lower jaws at c. 



Frequently these organs terminate in a fine point; at other times 

 their extremities are provided with cutting instruments, those of the 

 first pair always differing from those of the FlQ 2 22. 



second. Although organized to pierce the 

 tough cortex (bark) of plants, these animals 

 never refuse the more nutritive juices of ani- 

 mals if opportunity favor them, as every prac- 

 tical Entomologist knows to his cost, and 

 the pain resulting from the bite of many of 

 them is very severe. 



618. The best known insect of this order, 

 is the loathsome household tormentor, the 

 common bug (Cimex lectularius), and a figure 

 of its nutrimental organs is given (Fig. 222). 

 The mouth receives the secretion of two pairs 

 of salivary glands (h, i), in the form of sim- 

 ple follicles, terminated by minute vesicles Alimentary canal, Cimex 



7 lectularius. 



Upper portion of 

 mouth, Tree bug. 



Eostrum of 

 Tree bug. 



