FORM, GROWTH, AND CHANGE n 



c, st), with a smaller one at their junction ; the stipes bears a 

 sharp inner and a blunt outer lobe (called respectively the blade 

 or lacinia and the hood or galea) and a leg-like jointed palp 

 (Fig. 3, /, g, p). The mouth is bounded behind by a pair of 

 appendages in which parts corresponding to those of the 

 maxillae can readily be recognized, but which are joined 

 together by their bases so as to form a labium (Fig. 3 L) or 

 " lower lip." As this structure is, in grasshoppers and some 

 related insects, evidently connected with the cuticle of the 

 flexible neck-region between the head and thorax it may prob- 

 ably be regarded as belonging to the segment immediately 

 behind the head rather than to the head itself, with which, 

 however, it is closely knit in beetles and in most other insects. 



FIG. 4. HYPOPHARYNX OR TONGUE (Hy) AND MAXILLULAE (Ml) 



OF EARWIG (Forficula, A), AND BRISTLE-TAIL (Petrobius, B). 



In the latter, lacinia (I), galea (g), and palp (p) are recognizable, 

 x 20. 



The eyes, feelers, mandibles, maxillae and labium are recog- 

 nizable in the great majority of insects, and from their presence 

 we infer that at least five segments enter into the composition 

 of the head. Deeper study of the subject suggests the proba- 

 bility that other segments may, in some cases, be represented. 

 In the centre of the grasshopper's mouth there is a blunt 

 tongue (or hypopharynx) (Fig. 3 Hyp) with cuticle partly mem- 

 branous and partly firm, bearing a number of fine hairs ; on 

 the front face of this tongue a pair of narrow, elongate sclerites 

 (mxl) can be clearly seen. If, now, the tongue of an earwig 

 be examined for comparison it will be found that in a position 

 corresponding to that of the sclerites just mentioned, a pair 

 of prominent rounded lobes are attached by their bases to the 

 tongue and project beyond it (Fig. 4 A) . In a similar situation in 

 the mouth of some of the wingless spring-tails and bristle-tails, 



