ANATOMY OF INSECTS EXTERNAL' 



Hemiptera. In the Hemiptera, or bugs, the labium forms a long, 

 jointed beak, or rostrum (Fig. 15). This rostrum is cylindrical in 

 section, and its evolution from the type of labium found in the grass- 

 hopper may be understood by conceiving the labium of the latter 

 to be greatly elongated and then curled up on either side until the 

 lateral margins meet 

 on the median line 

 above, forming a su- 

 ture, as seen in the 

 hemipterous beak. At 

 the base of this suture 

 is found a triangular la- 

 brum closing the base 

 of the tube. The man- 

 dibles and maxillae are 

 long, bristlelike or 

 needlelike structures, 

 sharply pointed and 

 often bearing barbs at 

 the tip, and the max- 

 illae are locked to- 

 gether so as to form a 

 tube through which 

 the juices are sucked. 



Lepidoptera. The 

 moths and butterflies 

 possess a very different 

 style of sucking tube, 

 or proboscis, which is 

 curled up under the head like a watch spring. This is composed 

 of the two maxillae, whose inner faces are concave and which lock 

 together so as to form a tube which opens into the mouth. All 

 the other mouth-parts are almost entirely absent in most forms, 

 except the labial palpi. It is evident that this type of mouth-part is 

 only adapted to sucking nectar from flowers and is never injurious 

 to vegetation, while often adapted for pollenizing flowers which the 

 moths frequent. The caterpillars of moths and butterflies have 

 biting mouth-parts similar to those of the grasshopper. 



FIG. 19. Side view of head of a fly 

 a, antenna ; mxfl, maxillary palpus ; lab, labellum 



