i6 ADAPTATIONS OF INSECTS TO FLOWERS. [CH. 



and the legs. If we are asked why we assume 

 that in these cases the mouth and legs have been 

 modified, the answer is, that they depart greatly 

 from the type found in allied insects, and that be- 

 tween this original type and the most modified 

 examples, various gradations are to be found. 



The mouth of an insect is composed of (i) an 

 upper lip (Fig. 1 1 a), (2) an under lip (Fig. 1 1 d] 

 ^3) a pair of anterior jaws or mandibles (Fig. n &), 

 and (4) a pair of posterior jaws or maxillae (Fig. 

 1 1 c). These two pairs of jaws work laterally, 



FIG. ii. Mouth-parts of a Wasp a, labrum or upper lip ; b, mandibles ; c, maxilla; 



d, labium or lower lip ; xx, palpi. 



that is to say, from side to side, and not, as in man 

 and other mammalia, upwards and downwards. The 

 lower lip and maxillae are each provided with a pair 

 of feelers or palpi (Fig. n, c and d, x). The above 

 figures represent the mouth parts of a wasp, in which, 

 as is very usually the case, the mandibles are hard 

 and horny, while the maxillae are delicate and mem- 

 branous. In the different groups of insects, these 

 organs present almost infinite variations. 



