300 COMPARATIVE ZOOLOGY. 



(Ceranibycidce) ; and the destructive Weevils (Curculio- 

 nidce), with pointed snouts. 



5. Diptera, or " Flies," are characterized by the rudi- 

 mentary state of the hinder pair of wings. Although 

 having, therefore, but one available pair, they are gifted 

 with the power of very rapid flight. While a Bee moves 

 its wings one hundred and ninety times a second, and a 

 Butterfly nine times, the House-fly makes three hundred and 

 thirty strokes. A few species are wingless. The eyes are 

 large, with numerous facets. In some forms, as the House- 

 fly, all the mouth-parts, except the labium, are rudimen- 

 tary ; and the labium has an expanded tip, by means of 



FIG. 270. Metamorphosis of the Flesh-fly (Sarcophaga carnaria) : a, eggs; b, youug 

 maggots just hatched; c, d, full-grown maggots ; e, pupa; /, imago. 



which the fly licks up its food. In other forms, as the 

 Mosquito, the other mouth-parts are present as bristles or 

 lancets, fitted for piercing ; the thorax is globular, and the 

 legs slender. The larvae are footless grubs. The Diptera 

 number about twenty-four thousand. Among them are 

 the Mosquitoes (Culex)\ Hessian-fly (Cecidomyia\ so de- 

 structive to wheat; Daddy-long-legs (Tipula), resembling 

 a gigantic Mosquito ; the wingless Flea (Pulex) ; besides 

 the immense families represented by the House-fly (Mus- 



ca) and Bot-fly ((Estrus). 



6. Lepidoptera, or " But- 

 terflies" and "Moths," are 

 known chiefly by their four 

 large wings, which are thick- 

 ly covered on both sides by 

 minute, overlapping scales. 



FIG. 271. Scales from the Wiugs of vari- r & 



ous Lepidoptera. The scales are of different 



