148 



ANIMAL PHYSIOLOGY. 



[LESSON 42. 



FIG. 244. 



their rugous (wrinkled) surface the moisture contributing to make 

 them air-tight. In all these insects, the under lip is modified to 

 form the proboscis. The fleshy lips of the proboscis (a, 243), with 

 their rugous surface (6), are seen partly spread out for attachment. 



The lancets, &c., are shown in the figure 242. The long trian- 

 gular upper lip (a) covers the remainder of the apparatus ; on either 

 side are seen the upper jaws (b), which are, in this insect, blunt- 

 pointed : the under jaws (c) are curved like a scymitar, and remarka- 

 bly thin, and sharp at their points. In the Tabini, and all their 



allies, the upper jaws are sharp, 

 and lancet-shaped, while the under 

 jaws are blunt, or probe-pointed. 

 The long, leathery palpi (d) are 

 merely for additional protection. 



662. The pumping stomach at- 

 tains its highest development in 

 the Diptera; in them it consti- 

 tutes an independent organ, which 

 is beautifully exemplified in the 

 nutrimental organs of the Flesh- 

 fly (Musca carnaria), or Blue-fly. 

 In this insect (Fig. 244), the long 

 delicate oesophagus (a) is continu- 

 ed from the muscular crop, to the 

 end of the proboscis, but not all the 

 way as the oesophagus ; a some- 

 what wider tube is excavated in 

 the proboscis, at the commencement 

 of which the ducts of the salivary 

 glands (b, 5), and oasophageal tube, 

 proper, terminate. 



663. The salivary glands (c, c), 

 at their commencement, are robust, 



remarkably convoluted, tubes; by degrees they become straighter, 

 and attenuated (d, d), and finally end as delicate tubes, parallel with 

 the lower third of the stomach. 



664. The course of the oesophagus is direct to the commencement 

 of the crop, it then turns off, nearly at right angles, and ends in a 

 bladder-shaped bag, of large size the pumping stomach (e). 



665. It is easy to understand that the small quantity of air, al- 

 ways found in this receptacle, becoming rarefied so as fully to distend 



Nutrimental organs, Musca carnaria. 



