430 EXTERNAL ANATOMY OF INSECTS. 



This structure you will find in the stag-beetle, and some 

 other timber-devourers. Other Coleoptera have only a 

 process of a similar structure at each of the dorsal angles 

 of the base of the mandible, the intermediate one being 

 wanting ; and the articulation does not materially differ, 

 as far as I have examined them, in the Hymenoptera and 

 Neuroptera. In the Orthoptcra, the structure approaches 

 more nearly to that of the stag-beetle, since there are 

 three prominences : it is thus well described by M. Mar- 

 cel de Serres: " This articulation," says he, "takes place 

 in two ways. At first, in the upper surface of the man- 

 dible, and at its base, may be observed two small promi- 

 nences and a glenoid cavity ; these prominences are re- 

 ceived in two glenoid cavities excavated in the shell of 

 the front, as the cavity of the mandible receives a small 

 prominence of the same part. Below the mandible, and 

 at its base, there is a kind of condyle, which has its play 

 in a cotyloid cavity excavated in the shell of the temple, 

 far below the eye, and at the extremity of the coriaceous 

 integument of the head 3 ." Within the head in this or- 

 der, at least in Locusta Leach, is a vertical septum which 

 divides the head into two chambers, as it were, an occi- 

 pital and a frontal, consisting of a concave triangular 

 stem, terminating in two narrower concave triangular 

 branches, so as to resemble the letter Y, and forming 

 three openings, an upper triangular one, and two lateral 

 subquadrangular ones, which last are the cavities that re- 

 ceive the base of the mandibles. This partition, which I 

 would name Cephalophragma, doubtless affords a point of 

 attachment to many of the muscles of the head. It does 



a Comparaison des Organes de la Mastication des Orthoptics, 2. 



