ITS OUTER SKELETON. 45 



prism with an obliquely truncated end, upon which are many 

 fine hairs. A flexible and nearly transparent flap connects the 

 inner edges of the stipes and cardo, and joins both to the 

 labium. The muscles which move the bases of the maxillae 

 spring from the crura, central plate, and keel of the tentorium. 



On the posterior surface of the head, below the occipital 

 foramen, we find a long vertical flap, the labium, which extends 

 downwards to the opening of the mouth. It represents a 

 second pair of maxillre, fused together in their basal half, but 

 retaining elsewhere sufficient resemblance to the less modified 

 anterior pair to permit of the identification of their component 

 parts. The upper edge is applied to the occipital frame, but is 

 neither continuous with that structure nor articulated thereto. 

 By stripping off the labium upwards it may be seen that it is 

 really continuous with the chitinous integument of the neck. 

 The broad shield-like base is incompletely divided by a trans- 

 verse hinge into an upper and larger piece, the submentiim, and 

 a distal piece, the men turn. To the mentum are appended 

 representatives of the galese (here named paraglossa) and laciniae, 

 while a three-jointed palp with an additional basal joint (dis- 

 tinguished as the palpiger) completes the resemblance to the 

 maxilla3 of the first pair.* In front of the labium, and lying 

 in the cavity of the mouth is a chitinous fold of the oral 

 integument, the lingua, which lies like a tongue in the floor of 

 the mouth. The common duct of the salivary glands enters the 

 lingua, and opens on its hinder surface. The lingua is supported 

 by the chitinous skeleton represented in the figures of the 

 salivary glands. (Chap, vii., infra.) 



The epipharynx, which is a prominent part in Coleoptera and 

 Diptera, is not recognisable in Orthoptera. 



Functions of the Antennce and Mouth-parts. 



We must now shortly consider the functions of the parts just 

 described. The antennoo have long been regarded as sense- 

 organs, and even the casual observer can hardly fail to remark 

 that they are habitually used by the Insect to gain information 



* The homology of the labium with the first pair of maxillae is in no other Insects 

 so distinct as in the Orthoptera. 



