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AJV ECONOMIC ENTOMOLOGY. 



much more complicated in structure, and made up of a number 

 of more or less well-marked smaller pieces, which vary consider- 

 ably in form and shape according to the food habits of the insect. 

 Attached to each maxilla is a palpus^ or feeler, which often bears 

 organs of special sense, and is probably used by the insect to 

 recognize the character of its food. In function this maxilla is 

 auxiliary to the mandibles, which cut and tear the food, and de- 

 liver it in coarse shape to the maxillae. These assort and break 

 it up yet more to better its mechanical condition, and deliver it 

 to the labium, or lower lip, which also takes part in mixing the 

 food. There are great differences in this maxillary structure, 

 corresponding to the food habits ; and there may be teeth, 

 brushes, or other appendages suited to the requirements of the 

 insect. It is rarely necessary to study these in detail, and Fig. 3 

 illustrates sufficiently a typical form, with all the parts named. 



The labium, or lower lip, closes the mouth opening beneath, 

 forming its floor, on which is another sensitive surface, the hypo- 

 pharynx, which may be compared in function to the tongue of 

 the higher animals. As a rule, this labium is much less complex 

 than the maxilla, and it may be only a single piece or plate, 

 though, like the maxilla, furnished with a pair of palpi or feelers. 

 A typical labium is shown at Fig. 3, and the names of the parts 

 are given. Close study shows that originally the labium was 

 made up of just as many parts as the maxilla, but they have 

 grown together, in the course of time, for the more complete 

 closure of the- mouth opening. 



Insects with the mouth as above described, no matter what 

 their feeding habits, are always susceptible of being poisoned 

 through their food ; that is, they may be reached by means 

 of stomach poisons. Sometimes, of course, they feed in such 

 positions that we cannot apply the poison satisfactorily, — e.g., 

 inside of plant tissue ; but this does not alter their susceptibility ; 

 it simply means that we cannot take advantage of it. 



Of the haustellate or sucking mouth there are several varieties, 

 functionally quite diverse and indicating difference in habit. 



Butterflies and moths differ from all other insects in having the 

 mouth formed into a flexible tube, coiled like a watch-spring 

 under the head and between the labial palpi, which are the only 

 visible mouth appendages present. The mandibles have disap- 



