AN INSECT. 3 



placed in most cases between the large eyes. 

 The function of these rudimentary eyes is thought 

 to be limited to distinction of light from darkness. 

 They are well seen on the head of the cicada as 

 3 tiny sparkling "gems" between the compound 

 eyes. (Plate i. Fig. 3a.) (3) Mouth Parts: The 

 mouths of insects vary according to their methods 

 of obtainino- food and their habits. The more 

 normal mouth of insects is the biting mouth (Plate 

 I, Fig. 2). It consists of an upper lip: the labrum; 

 a pair of stout jaws, called mandibles, stand promi- 

 nently below the labrum or upper lip : these are 

 seizing, tearing and biting jaws. There is a pair 

 of outer flexible chewing jaws called first or outer 

 maxillae; there are usually 2 teeth present on each 

 maxilla, and a long five-jointed palpus (often called 

 palp). There is an inner pair of maxill?e with three- 

 jointed palpi ; these jaws are usually fused to form 

 a solid central and posterior basal lip called gener- 

 ally the labium. The palpi or palps are used as 

 fingers to direct the food towards the mouth and to 

 aid in holding food. 



In the case of insects with purely sucking habits, 

 the mouth is modified to form a sucking 

 tube which consists of 2 long half tubes which, 

 V hen placed together, form a sucking apparatus. 

 (Plate 38. Figs. 5, 6, 7.) In other insects the 

 piercing and sucking mouth is represented by a 

 certain number of setae or bristles (formed by a 

 modification of the mouth parts) which are placed 

 close together to form a canal (Plate 41, Fig. i). 

 The tips of the setge pierce a leaf, or body of an 

 insect, etc., and the moisture is drawn through the 



