EXTERNAL STRUCTURE OF INSECTS. 29 



ning accustom himself to observe their character in every 

 insect which comes before him, always remembering, how- 

 ever, that there is often much difference between the an- 

 tenna of the male and female, even in the same species. 



The mouths of insects, as might be expected, afford a 

 most interesting variety of structure, being adapted not 

 only to the various nature of the food proper for the 

 different species, but also to their various modes of 

 life. Thus, among the architectural species, parts of 

 the mouth are so modified as to act as spades, trowels, 

 &c. ; to the upholsterers they are scissors ; in the chase 

 they seize and hold the prey, while the warlike tribes 

 find in them powerful weapons of offence. 



The principal parts of the mouth are six ; the upper 

 and lower lips, and two pairs of jaws, those of each pair 

 acting upon each other, from side to side. 

 An idea of the arrangement of the mouth 

 may be formed from the accompanying 

 diagram, in which A represents the upper 

 lip, or labium ; B, the lower, or labrum; c c, 

 the upper pair of jaws, or mandibles; d d, 

 the lower pair, or maxillas. (See also fig. 6, p. 32.) 



Insects are divided primarily into biting and suck- 

 ing insects, and while the parts just named are easily 

 recognised in the first division, they are in the second 

 so differently developed and modified as to be hardly 

 traceable, except by such a process as that described 

 in chap, i., for tracing the relationship between the 

 horse's foreleg, the bird's wing, and the arm of a man. 



The mouth of a beetle affords an excellent example 

 of all these parts, as they are found in biting insects 

 Fig. 3 represents the top of the head of a Tiger- 

 beetle (PL I., fig. 1), and shows the situation of the 



c c 



d d 



