INSECTS IN GENERAL 3 



the insect's mouth-parts, or " jaws," of which there 

 are three distinct pairs. There is reason for thinking 

 that these three pairs of mouth-parts trace their origin 

 to a corresponding number of appendages which 

 belonged to segments behind the head-lobe of the 

 early ancestral stock. Nature, in fact, seems to have 

 " telescoped" the parts, with the result that the 

 "head" of the modern insect includes several rings, 

 or segments, that were quite distinct therefrom in its 

 remote progenitors. Possibly these archaic beings 

 developed an appetite for harder foods than they had 

 erstwhile eaten. Be this as it may, there seems no 

 room for doubt that certain of their body-rings were 

 pushed gradually forward, so to speak, into the im- 

 mediate neighbourhood of the mouth, and that the 

 appendages carried by these rings were turned in- 

 wards, so that each pair could be used for nipping and 

 biting. This is why the above-cited group of animals 

 (including insects) is called Gnathopoda, or " foot- 

 jawed." 



In the case of an insect, such as a cockroach or a 

 cricket, which subsists upon solid food, the position of 

 the mouth-parts is not difficult to make out. There is 

 first a kind of plate, called the upper lip, or labrum. 

 This is hinged to the head in the middle line, and 

 behind it are the three pairs of jaws, or foot-jaws, 

 termed in the order of their arrangement the mandibles, 

 the first maxilla, and the second maxilla. The mandibles 

 are powerful nipping organs, specially designed for 

 breaking up hard or tough substances. The maxillae 

 of both pairs are much more delicate structures, and 

 probably serve to mince the food finely, or to pass 

 suitable fragments into the mouth i.e., the opening 

 which leads to the gullet. Unlike the mandibles, each 



