86 ZOOLOGY. 



(1) the Head, bearing the eyes, feelers (antennae), and 

 jaws ; (2) the Thorax, composed of three fused seg- 

 ments, of which the first (prothorax) bears a pair of 

 legs, while the second (mesothorax) and third (meta- 

 thorax) not only bear a pair of legs each, but also 

 sometimes a pair of wings in addition; (3) the 

 Abdomen, which possesses no limbs, and of which 

 the number of segments is not always the same. 

 These three regions of the body perform diflFerent 

 functions ; the head is concerned with sensation and 

 the taking up of food, the thorax with movement, 

 while the abdomen contains the organs of digestion 

 and reproduction. I will now deal somewhat more 

 fully with the difierent body-regions of an insect. 



Head. — Almost all insects have in the adult state 

 a compound eye, i.e. an eye made up of a large number 

 (up to ten thousand) of smaller eyes. In many insects 

 one finds in addition to this a few simple eyes on the 

 top of the head. The feelers are very unlike in 

 different insects ; they serve as organs of touch, and 

 perhaps also help some other sense. The mouth-parts 

 consist of three pairs of jaws, of which the first (the 

 mandibles) and the second pair (maxillae) are freely 

 movable from side to side, while the third consists of 

 two jaws immovably fused together (lower lip, or 

 labium). A downward projection of the skin of the 

 head (the upper lip, or labrum) overhangs the three 

 pairs of jaws (Fig. 58). In insects which feed on 

 solid matters, tearing or chewing them, the jaws are 

 short and sharp-edged (biting mouth-parts) ; in those 

 which take up fluid food (blood, the juices of plants, 

 etc.) they are elongated, and adapted for Licking, 

 sucking, or piercing. 



Thorax. — The names of the parts of the legs are 

 for the most part those used in the case of mammalian 

 limbs ; though the similarity between the limbs of 

 Mammals and Insects is quite superficial. The follow- 

 ing parts are distinguished in the leg of an insect : 



