MOUTH AND MOUTH PARTS OF A BEETLE. 



9 



Oftentimes, and especially in the greater number of Rhyncho- 

 phora or snout beetles (not included in this paper), the front is 

 prolonged so that the distance between the eyes and mouth parts is 

 greater in length than the rest of the head. This prolonged por- 

 tion is called the rostrum or leak, and it usually has on each outer 

 side a groove or serobe, varying much in length and used for the 

 reception of the long basal joints of the antennae when in repose. 



In most beetles the front is short and the portion in front of the 

 suture is called the clypeus. This varies much in form and size, 

 being sometimes prolonged so as to extend over the mouth. When 

 small it is by some authors called the epistoma. Its form, texture 

 and the character of its front margin, whether dentate, sinuate, 

 truncate, etc., are much used in classification, especially in the fam- 

 ily Scarabasidaa. 



The under surface of the head in front is variably excavated to 

 form the mouth. The parts beneath the eyes and behind the man- 

 dibles forming the side borders of the mouth are the genre or cheeks. 

 From the opening of the mouth two seams or sutures may usually 

 be observed running backwards. These are the gular sutures, and 

 they of ten converge at middle but separate at either end. 



The Mouth and Mouth Parts. In front of or below the clypeus 

 and above the mouth there is usually a small movable flap, called 

 the labrum or upper lip. It is variable in form, is joined to the 

 clypeus and is sometimes almost or completely hidden by the latter. 

 In the majority of Rhynchophora the labrum is entirely wanting. 



Immediately below the labrum are the jaws or mandibles. They 

 also vary much in shape and size but are usually curved, often 

 toothed on the inner side, and, in certain males, especially those of 

 the Lucanida?, are long and often bear prongs, thus resembling 

 somewhat the antlers of a deer. In a number of genera, as those of 

 some Carabida?, the mandibles have a groove or scrobe on the outer 

 side, and this often bears a large puncture from which arises an 

 erect seta or bristle-like hair. The mandibles of beetles are so 

 formed and attached to the epi cranium as to move only in and out 

 or to and from a median line. They are used for prehending, cut- 

 ting, tearing and crushing the food; also often for defense, and 

 rarely as clasping organs. Their range of action is often increased 

 by movements of the entire head, which are permitted by the loose 

 union of the head and thorax. 



Attached to the sides of the head just below or behind the man- 

 dibles is a pair of aiding or accessory jaws called maxillce. Each 



