ANATOMY AND PHYSIOLOGY 



39 



maxilla consists of three lobes, namely, palpus, galea and 

 lacinia, which are borne by a stipes, and hinged to the skull 

 by means of a car do. The palpus, always lateral in position, 

 is usually four- or five-jointed and is tactile, olfactory or gus- 

 tatory in function. The lacinia is commonly provided with 

 teeth or spines. The maxillae supplement the mandibles by 

 holding the food when the latter open, and help to comminute 

 the food. Additional maxillary sclerites, of minor impor- 

 tance, often occur. 



The labium, or under lip, may properly be likened to a united 

 pair of maxillae, for both are formed on the same three-lobed 

 plan. This correspondence is evident 

 in the cockroach, among other gener- 

 alized insects. Thus, in this insect 



(Fig. 44) : 



LABIUM = MAXILLA 



palpus = palpus 

 paraglossa = galea 



glossa = lacinia 

 palpiger = palpifer 

 mentum = stipites 

 submentum with gula = cardincs 



FIG. 47. 



In most mandibulate orders the 

 glossae unite to form a single median 

 organ, as in Harpalus (Fig. 47, g). 

 The labium forms the floor of the 

 pharynx and assists in carrying food 

 to the mandibles and maxillae. 



The use of the term " second 

 maxillae " for the labium of an in- 

 sect is open to objection, as it implies an equivalence with 

 the second maxillae of Crustacea which is by no means 

 established. 



The tongue, or hypopharynx, is a median fleshy organ (Fig. 

 44) which is usually united more or less with the base of the 

 labium. In insects in general, the salivary glands open at the 



Labium of Harpalus caligi- 

 nosus, ventral aspect. g, 

 united glossae, termed the 

 glossa; m, mentum; p, palpus; 

 pg, palpiger; pr, paraglossa; 

 sm, submentum. The median 

 portion of the labium beyond 

 the mentum is termed the 

 ligula. 



