ORIGIN OF SUCIUNG MOUTH-PARTS. 



183 



210. Mouth-p.irts of the 

 House fly. 



are converted in the male into simple clasping organs. And to 

 omit a number of instances, in the suctorial Heraiptera or bugs 

 we have diiferent grades of structure in the mouth-parts. In 

 the biting lice (Mallophaga) the mouth is mandibuhite, in the 

 Thrips it is mandibulate, the jaws being free, and the maxillas 

 bearing palpi, while the Pediculi are 

 suctorial, and the true bugs are emi- 

 nently so. But in the bed bug it is 

 easy to see that the beak is made up of 

 the two pairs of jaws, which are sim- 

 ply elongated and adapted for piercing 

 and sucking. Among the so-called 

 haustellate insects the mouth-parts 

 vary so much in different groups, and 

 such different organs separately or 

 combined perform the function of 

 sucking, that the term haustellate 

 loses its significance and even mis- 

 leads the student. For example, in 

 the house fly the tongue (Fig. 210 I, 

 the mandibles, m, and maxillae, mp, are useless), a fleshy pro- 

 longation of the labium or second maxilla, is the sucker, while 

 the mandibles and maxillae are used as lancets by the horse fly 

 (Fig. 211, m, mandibles, mx, maxillaj). The maxillae in the but- 

 terfly are united to form the sucking tube, while in the bee the 

 end of the labium (Fig. 212) is specially 

 adapted for lapping, not sucking, the nectar 

 of flowers. But even in the butterfly, or 

 more especially the moth, tliere is a good 

 deal of misapprehension about the structure 

 of the so-called "tongue." The mouth-parts 

 of the caterpillar exist in the moth. The 

 mandibles of the caterpillar occur in the 

 head of the moth as two sma'll tubercles 

 (Fig. 213, m). They are aborted in the 

 adult. While the maxillae are as a rule 

 greatly developed in the moth, in the cater- 

 pillar they are minute and almost useless. The labium or sec- 

 ond maxillae, so large in the moth, serves simply as a spinneret 

 in the caterpillar. But we find a great amount of variation in the 

 tongue or sucker of moths, and in the silk moths the maxillae 



211. Mouth-parts of 

 Horse fly. 



