THE AX ATOMY OF IX SECTS. 15 



name applied by Kirby and Spence to it and to the other claw-like projections 

 of the maxilla. The French entomologists distinguish it as k prema.villaire. 

 her of these names is desirable ; the former is not restricted to this part of 

 the maxilla, but is often applied to the terminal portion of the lacinia ; the latter 

 name is objectionable both in form and signification ; it is hardly appropriate 

 to apply the prefix pra to the most distal part of an appendage. I propose, 

 therefore, the name digitus for this sclerite. 



The Labium or Second Maxilla:. The labium or under lip (12) is attached to 



the cephalic border of the gula, and is the most ventral of the mouth parts. It 



are to be a single organ, although sometimes cleft at its distal extremity ; 



however, composed of a pair of appendages grown together on the middle 



line of the body. In the Crustacea the parts corresponding to the labium of 



insects consist of two distinct organs, very closely resembling the maxilla:. In 



this case they are termed the second maxilla?, a name which is sometimes 



applied to the labium of insects. Hence in defining the Hexapoda it is stated 



that they have two pairs of maxillae. 



In naming the parts of the labium, entomologists 



ally taken someform of it in which the two 



completely grown together, that is, one 



h is not cleft on the middle line (Fig. 29). 



:i first describe such a labium, and later one 



in which the division into two parts is carried as 



far as we find it in insects. 



The labium is usually described as consisting of 



, . FIG. 29. Labium of Harfalut. 



three principal parts and a pair of appendages. The 



principal parts are the submentum, the mcntitm, and the ligula ; the appendages 



are the labial palpi. 



The basal part of the labium consists of two transverse sclerites ; the prox- 

 imal one, which is attached to the cephalic border of the gula, is the submcn- 



This is often the most prominent part of the body of the labium. 

 The Mfntum (l>) is the more distal of the two primary parts of the labium. 

 It is articulated to the cephalic border of the submentum, and is often so 

 slightly developed that it is concealed by the submentum.* 



!udes the remaining parts of the labium except the labial 

 palpi. It is a compound organ ; but in the higher insects the suture- 



tiich it is composed are usually obsolete. Three 

 parts, however, are commonly distinguished < Fig. 29), a central j. 

 greatly prolonged, tin- .d two parts, usually small membranous 



ections, one on each side of the the id ns sa. the /. 



* I'nfortunately the term mrntum is applied by some entom< 

 turn, and the true n distinguished by a different i 



is the case in one of the n in tin- literature of American etitn- 



igr, "The Clav and 



: he student in the use of this indispensable wikmust U-ar thi^ change <>t names 



in ir. c authors have termed the true nimtum the 4 r/v s 7, ','//>. and state tli.it in 



the Carabtdse the homologous portion is often called the " basal membrane <>( ti,> 



(/. c. p. x. 



