28 THE CLASS OF INSECTS. 



inserted on the under side of the head and just behind the 

 mouth. The maxilla consists of a basal joint, or cardo, 

 beyond which it is subdivided into three lobes, the stipes, or 

 footstalk ; the pdlpifer, or palpus-bearer ; and the lacinia, or 

 blade. The stipes forms the outer and main division of the 

 organ. The lacinia is more membranaceous than the other 

 parts, and its upper surface is covered with fine hairs, and 

 forms a great part of the side of the mouth. It is divided 

 into two lobes, the superior of which is called the galea, or 

 helmet, which is often a thick double-jointed organ edged with 

 stiff hairs, and is used as a palpus in the Orthoptera and many 

 Coleoptera. The inferior lobe is attached to the internal angle 

 of the lacinia. It terminates in a stiff minute claw, and is 

 densely covered with stout hairs. The maxilla^ palpi are 

 long, slender, one to four-jointed organs. In Perla I have found 

 that both pairs of palpi bear organs probably of smell. 



The maxillae vary greatly in the different groups. Their office 

 is to seize the food and retain it within the mouth, and also to 

 aid the mandibles in comminuting it before it is swallowed. 

 This function reminds us of that of the tongue of vertebrate 

 animals. 



The labium, or second maxillce (Fig. 40), is placed in front of 

 the gula, which forms the under part of the head, and is bounded 

 a on each side by the gence, or cheeks, and 

 f]T\ posteriorly by the occiput. The genae are 

 \ J bounded laterally by the eplcranium and 

 LJ the under side of the eyes. In front are 

 **& 40 - situated the basal parts of the labium, or 



second maxillae, which embraces the submentum and mentum 

 (or labium proper). The labial palpi are inserted into the 

 mentum, but often the latter piece is differentiated into two, 

 the anterior of which takes the name of palpiger, called by 

 Dr. Leconte (Smithsonian Miscellaneous Collections) the ligula, 

 and from which the palpi originate. The ligula is the front 

 edge of the labium, being thfe piece forming the under lip. 

 It is often a fleshy organ, its inner surface being continuous 



FIG. 40. Ligula and labial palpi of AmpMzoa, an aquatic beetle. It is quadrate 

 and without paraglossae; a, mentum of the same, being deeply incised, and with a 

 tooth at the bottom of the excavation. From Horn. 



