EXTERNAL ANATOMY OF INSECTSr 457 



at the base, the two molary plates (molce), which in this 

 genus are narrow, transverse and not furrowed, are so 

 applied as evidently to have an action upon each other, 

 as the mandible opens and shuts, proper for trituration. 

 Within these is the base of the tongue, under the form 

 of a ventricose sack. The upper part of this last organ, 

 which forms the internal covering of the labium, appears 

 to consist of three (in the recent insect jleshy) lobes, the 

 middle one being bent downwards internally, so as to 

 form a kind of sloping cover to an orifice in the part 

 I call the base. After two or three days, the tongue 

 shrinks and dries to a hard substance; — between the man- 

 dibles and the base of the tongue I could not discover 

 the pharynx. The above apparent opening covered by the 

 tongue was the only one I could perceive. In the latter 

 case, the form and structure of the base of the tongue is 

 more visible: it is an oblong ventricose tubular sack, 

 projecting above anteriorly into an acute angle formed 

 by a fine white membrane, most beautifully and deli- 

 cately striated with oblique striae, to be seen only under 

 a powerful lens : on the anterior side of this sack are two 

 parallel cartilaginous ridges close to each other, fringed 

 with short hairs, which take their origin from the angle. 

 I could not be certain whether the orifice covered by 

 the intermediate lobe was only apparent, or real ; but I 

 did not succeed in my endeavour to find any other pha- 

 rynx, though from the molary structure of the base of 

 the mandibles one may conjecture that there must be one 

 situated at the base of this sack to receive the food they 

 render after trituration. The excrement of this animal 

 is not fluid. In the Libellulina the pharynx seems 

 closed by two valves meeting. This part in Hymeno- 



