STRUCTURE AXD CLASSIFICATION. 



15 



Fig 



or upper jaws are distinct and prominent. They work horizon- 

 tally, from side to side, instead of vertically, or up and down, as is 

 the case in the higher animals, and their form and general shape 

 often furnish an indication to the character of the species, — that is, 

 whether it is predace- 

 ous, living upon ani- 

 mal food, or whether 

 it is phytophagous, 

 feeding upon plant 

 tissue. This alone, in 

 some orders, suffices 

 to tell us whether we 

 have to deal with a 

 friend or an enemy. 

 If the jaws are rather 

 long, sharp-pointed, 

 with slender, sharp 

 teeth on the inner side 

 (Fig. 3, c, d), it may 

 be safely classed as 

 predaceous ; if they 

 are broad, stout, con- 

 cave within, the edges 

 meeting broadly, even 

 if toothed, or if they 

 are gouge-shaped 

 (Fig. 3, a, e), we can 

 say with great confi- 

 dence that the species feed upon vegetable tissue. Of course 

 some uncertainty may result in intermediate types (Fig. 3, b) ; 

 but the rule holds good generally, and where it leaves a doubt, 

 some other character will readily determine the question. 



Formiing the front of the mouth and covering the base of the 

 mandibles is the upper lip, or labrum ; on the inner side of which 

 there is usually a sensitive structure, the epipharynx, which con- 

 tains the organs of taste, and corresponds as nearly as may be to 

 the palate in higher animals. It has no special function in feed- 

 ing, and often seems to form part of the front of the head itself 



Below the mandibles we have a second pair of jaws or 77iaxillce^ 



Mouth parts of a mandibulate insect : different types 

 of mandibles at a, b, c, d, e ; f, the labrum-epipharynx ; 

 g, k, types of maxillge ; the cardo at c ; stipes, st ; sub- 

 galea,^^-; galea as marked ; palpus bearer, //r; palpus 

 2Xmxp; lacinia at/ac; and digitus at ^f?^ ,■ z, the labium 

 with sub-mentum, S7n, mentum, m, ligula, lig, para- 

 glossa,/>ar, and palpi. 



