LESSON 40.] NUTKITION IN INSECTS. 141 



of them, are of great length (two inches long). The end of this 

 compound instrument is thrust deep into the coveted fluid, and 

 almost immediately the creature is on the wing again ; the sip has 

 been taken, the appetite is appeased. 



633. The structure of the under jaws, when made straight, is 

 very curious. 



Each one is a hollow tube, and the junction of the two forms 

 another, so that the apparatus consists of three tubes. The outer 

 surface is ringed, and each tube is really a tube and a half. To pro- 

 tect these important organs, a pair of inordinately large feelers are 

 found connected to the lower lip labial palpi therefore (c). 



634. The oesophagus (as will be seen hereafter) is divided into 

 two branches, each one of which occupies an under jaw, so that either 

 might act independently of the other. The central canal, formed 

 by the junction of the two under jaws, receives and transmits the 

 secretion of the salivary glands ; so that the FIG. 234. 

 central tube is used to insalivate the food which 



is sucked up by the two under jaws. The 

 under lip is much larger than the upper, but of 

 variable size. 



635. The alimentary canal of the Cabbage 

 Butterfly (Pontia Brassica) is shown in Fig. 

 234. 



636. The oesophagus (a), cut off below the 

 bifurcation, receives the tube connected with 

 the pumping stomach (c), and the food is re- 

 ceived into the stomach (d). The salivary glands 

 (n, ri), in this insect, are simple filiform tubes. 



Below the pylorus, the bile vessels are con- 

 nected to the commencement of the Ileum (e) ; 

 the former are very delicate, and of great 



, , 7 >. Nutrimental organs, Pon- 



extent (k). tia Brassica. 



The ccecum is seen (g) arising from the colon (h). 



LESSON XL. 



NUTEITION IN INSECTS, CONTINUED. 



637. In the larval condition (maggots, caterpillars, and grubs) 

 of insects, the nutritive organs are straight in their direction, and 



