TARTS OF THE MOUTH OF INSECTS. 



311 



trivance than in that before us : jaws armed with strong and penetrating 

 hooks for seizing and securing active and struggling prey sharp and 

 powerful shears for clipping and dividing the softer parts of vegetables 

 saws, files, and augers for excavating and boring the harder parts of 

 plants lancets for piercing the skin of living animals siphons and 

 sucking-tubes for imbibing fluid nutriment all these, in a thousand 

 forms, are met with in the insect world, and thus provide them with the 

 means of obtaining food adapted to their habits, and even of construct- 

 ing for themselves edifices of inimitable workmanship. 



(818.) Parts of the mouth. The mouths of insects may be divided 

 into two great classes : those which are adapted for biting, forming 

 what is called a perfect or mandibulate mouth ; and those which are so 

 constructed as only to be employed in sucking, constituting the suctorial, 

 haustellate mouth. It is in the former of these divisions that all the 

 parts composing the oral apparatus are most completely developed ; we 

 shall therefore commence by describing the different pieces of which a 

 perfect mouth consists, viz. an upper and an under lip, and four horny 

 jaws. We select the mouth of the Dragon-fly (fig. 155, A) as an example. 

 The upper lip (labrum, B) is a somewhat convex corneous plate, placed 

 transversely across the upper margin of the cavity wherein the jaws are 



Fig. 155. 



Parts of the mouth of a Dragon-fly. 



lodged, so that, when the mouth is shut, it folds down to meet the 

 under lip (labium), and these two pieces more or less completely con- 

 ceal the proper jaws, which are lodged between them. 



(819.) The upper pair of jaws (mandibulce) are two hard and powerful 

 hooks (fig. 155, c), placed immediately beneath the upper lip, and so 

 articulated with the cheeks that they move horizontally, opening and 

 shutting like the blades of a pair of scissors. Their concave edge is 



