4-40 EXTERNAL ANATOMY OF INSECTS. 



liable to variation than almost any other organ, as Mr. 

 W. S. MacLeay has judiciously observed, there seems 

 good reason for employing them — it is therefore of im- 

 portance that you should be well acquainted with them. 

 Their situation is usually below each mandible, on each 

 side of the labium; towards which they are often some- 

 what inclined, so that their tips meet when closed. In 

 some cases, as in the Predaceous beetles (CarabusJa. &c), 

 they exactly correspond with the mandibles; but in others 

 their direction with respect to the head is more longitu- 

 dinal, as in the Hymenoptera, &c. In substance they 

 may be generally stated to be less hard than those or- 

 gans ; yet in some instances, as in the JLibellidina, Ano- 

 plognathidcc, &c. they vie with them, and in the Scara- 

 baeidai and Cetoniada? exceed them, in hardness. In the 

 bees, and many other Hymenoptera, they are soft and 

 leathery. Their articulation is usually by means of the 

 hinge on which they sit : it appears entirely ligamentous, 

 and they are probably attached to the labium at the 

 base, or mentum — at least this is evidently the case with 

 the Hymenoptera, in which the opening of the maxillae 

 pushes forth the labium and its apparatus. In that re- 

 markable genus related to the glow-worms, now called 

 Phengodes {JLampyris plumosa F.), and in the case-worm 

 flies (Tric/wptera K.), the maxilla; appear to be connate 

 with the labium, or at least at their base. — As to their 

 composition, these organs consist of several pieces or por- 

 tions. At their base they articulate with a piece more 

 or less triangular, which I call the hinge (Cardo) z . This 

 on its inner side is often elongated towards the interior 



a Plate VI. Fig. 3, 6, 12. VII. Fig. 3. e". 



