THE CATERPILLAR. 15 



mandibles, pyramidal, horny pieces, the chiselled 

 or serrated edge of the one playing against that 

 of the other as they work laterally. The mouth 

 lies between them, and they are followed by more 

 complicated parts, the secondary jaws, or so-called 

 maxillae, which in many insects have a similar 

 movement, and play no doubt a considerable part 

 in the preparation of the food ; but here they 



FIG. 21. Head of caterpillar of Danais Plexippus ; a, front view ; b, side 

 view, both x 3 ; c, view from beneath, x 10; Ib, labrum : md, mandible; 

 mx, maxilla, with two palpi ; Im, labium, with one pair of palpi ; s, spinneret ; 

 a, antenna (the bristle is not shown) ; o, ocelli (Burgess). 



have only a certain telescopic motion of with- 

 drawal and protrusion ; they consist of a pair of 

 rounded, fleshy, semi-globular prominences, and 

 each of these has two appendages or feelers called 

 palpi, the outer and larger composed of several 

 joints, the inner of only one. The rest of the 

 under and hinder part of the head is taken up 

 with the labium or under lip and its appendages ; 

 though called in common language the under lip, 

 it should not be compared or contrasted with the 

 upper lip, but with the maxillae or secondary 

 jaws, being in all insects of a similar composition, 



