GENERAL CHARACTERS 



the proboscis is not a single tube, but, although so remarkably thin, 

 is really a set of three distinct pipes, one lying on each side of the 

 central one. It is said that the central tube only is used for suck- 

 ing up the liquid food, and there seems to be some doubt as to the 

 uses of the other two. Some naturalists are of opinion that the 

 latter are air tubes, and are connected with the respiration of the 

 insect ; while others say that through these the insects eject a thin 

 watery fluid with which to dissolve or dilute those sweetmeats 

 that are not sufficiently liquid to be readily sucked up. But possi- 

 bly both these opinions are correct, the proboscis serving all three 

 of the purposes here named. The only observation of my own 

 bearing on the subject is this. While a moth was feeding on a 

 drop of syrup in a strong light, a powerful lens revealed drops 

 of liquid, mingled with bubbles of air, passing 

 alternately up and down the two lateral tubes of 

 the proboscis. At the same time the upward 

 current of syrup in the central tube was by no 

 means steady and continuous. 



When this organ is not in use, it is beautifully 

 coiled into a close spiral which lies between the 

 labial palpi. The length varies considerably in 

 different insects, and consequently the number of 

 turns in the spiral must differ also. Sometimes 

 there are less than two turns, while some of the 

 longer ones form spirals of from six to ten turns. 



In concluding our brief account of the head 

 of lepidopterous insects it is, I suppose, hardly 

 necessary to add that there is no kind of chewing 

 apparatus to be described ; all the members of this order, at least in 

 the perfect state, deriving the whole of the little nourishment they 

 require entirely by suction through the proboscis or * trunk.' 



The second division of the body is the thorax. This is much 

 larger than the head, and consists of three ring-like segments, 

 joined one behind the other so intimately that the lines of junction 

 are hardly visible, even after the thick clothing of fine hair has been 

 brushed off. Behind the thorax is the abdomen, which is composed 

 of several segments, the junctions between the rings often being 

 most distinct. 



From the sides of the thorax proceed the two pairs of wings, the 

 general structure of which we have already to a certain extent 

 examined. But when we are a little farther advanced in our 



FIG. 7.- SECTION 

 OF THE PRO- 

 BOSCIS OF A 

 BUTTERFLY. 



