Head 7 



by inpushing of the skin, which gives attachment to the 

 muscles used in moving the head and jaws (fig. 5) (i). 



These various parts of the head-skeleton vary 

 greatly in different insects. The Cockroach's head, 

 as we have seen, is elongated from above downwards, 

 consequently the face and upper lip are largely de- 

 veloped. But in many Beetles the head is elongated 

 from behind forwards, and in this case the epicranium 

 and giila (a sclerite beneath the head, absent in the 

 cockroach) are greatly extended, while the face is 

 much reduced and the labrum is often absent. In 

 the cockroach the eyes occupy relatively only a small 

 portion of the head-surface. But in insects of rapid 

 flight, these organs being of the greatest importance, 

 become much enlarged ; in Moths the eyes occupy 

 nearly all the side regions of the head, while in some 

 two-winged Flies and Dragon-flies they overspread the 

 top of the head as well, touching each other along 

 the middle line. The heads of such insects as these 

 tend to become globular in form (fig. lo). 



Except for a few bristles on the upper lip, the 

 Cockroach's head is smooth and naked. But in very 

 many insects the surface is ridged and furrowed, or 

 pitted ; while it is often clothed in the same way as the 

 rest of the insect's body, with a dense hairy covering, 

 as in Bees (fig. 15), or with the modified flattened 

 hairs known as scales, as in Springtails and Moths. 



The epipharynx (2), which in the Cockroach forms 

 a lining to the roof of the mouth, is in the Bee (fig. 

 15^) visible outside. It becomes greatly lengthened 

 and chitinised in some Flies and Fleas, forming, with 

 the upper lip, a formidable piercing-organ (fig. 8). 



Appendages of the Head. — We have noticed that 

 an insect's body is built up of a number of segments 

 situated one behind the other. At first sight it might 

 seem that the head must be regarded as the foremost 



