6 ELEMENTARY LESSONS ON INSECTS 



on the middle line of the head and a pair beside and be- 

 hind it. 



The antennae are attached in front. Their function is 

 fairly expressed by the name of "feelers" that is often 

 given them. 



The mouthparts are built on a plan of four: an upper lip 

 hanging down from above, a lower lip rising up from below, 

 the two together covering two pairs of jaws that swing 

 laterally between. 



The upper lip or labrnm is of simple structure. It is a 

 broad chitinous flap-like covering plate hanging free below. 



The upper pair of jaws, called mandibles are the heavy 

 chewing organs. Each is a single piece, incurved to the 

 toothed tip, heavily chitinized and strongly joined to the 

 head on a stout basal hinge. 



The lower jaws, called maxillae (singular maxilla) are 

 chewing organs of a lighter build, and of a much more 

 complicated structure. They are composed of a number of 

 segments as follows: there are two basal segments (cardo 

 and stipes) that together uphold three appendages, the 

 tips of which may be seen without dissection. The inner- 

 most of these appendages (the lacinia) is most like the 

 mandibles, being rather heavily chitinized and toothed 

 at its tip and used for chewing. The outermost appendage, 

 the palp or palpus (plural palpi), is a free, five-jointed 

 appendage, somewhat like a small antenna. It is a food 

 "feeler." 



