60 THE BUTTERFLY. 



some to form the sucking tube, in which case the 

 insect might be said to have two mouths, for there 

 would be two entrances to the oesophagus. This, 

 however, is not the case, the interior of each lat- 

 eral half being filled with muscles, tracheae, and 

 nerves for the movement of the organ. The rings 

 of which it is composed are made up of a great 

 number of plates, united by the more yielding 

 part of the cuticle, allowing of great freedom of 

 motion. These rings throw off, at the points 

 where the convex and concave sides meet, a series 

 of oblique, curving plates or hooks, which, when 

 the two maxillae are brought together, interlace 

 in the most complete manner, to form a perfectly 

 flexible yet impervious tube. The outer walls of 

 the lateral tubes are supplied with curious papil- 

 lae of greatly varying shapes, size, and abundance 

 in different groups [see Figs. 178, 179], but, in 

 general, more highly organized and abundant in 

 the highest family. These must probably be re- 

 garded as organs of taste. Within either half of 

 the maxillae, oblique muscles exist [Fig. 69] serv- 

 ing to coil the whole into the watch-spring-like 

 form in which it is packed away when at rest. 



But now that we comprehend the structure of 

 this wonderful piece of mechanism, and can ap- 

 preciate the change that has been wrought in its 

 development from an utterly simple, almost 

 microscopic joint, do we understand any better its 



