154 INVERTEBRATE ANIMALS. 



tails" (Podurce), which are commonly found under stones or 

 in cellars and such like situations. They are distinguished by 

 having the extremity of the abdomen furnished with bristles, 

 by the sudden straightening of which the insect can effect pow- 

 erful leaps. In many cases the body is covered with delicate 

 scales which form beautiful objects under high powers of the 

 microscope. 



SECTION II. HEMIMETABOLIC INSECTS. Metamorphosis 

 incomplete ; the larva differing from the perfect insect chiefly 

 in the absence of wings and in size ; pupa usually active, or, 

 if quiescent, capable of movement. 



ORDER IV. HEMIPTERA (Gr. hemi, half; pteron, wing). 

 In this order the mouth is formed for suction ; the eyes are 

 compound, but simple eyes are often present in addition. Two 

 pairs of wings are always present. 



The Hemiptera live upon the juices of plants or animals, 

 which they are enabled to obtain by means of their suctorial 

 mouths. All the four wings are generally present, but the 

 condition of these varies in different sections of the order. In 

 one group all the four wings are membranous (Fig. 65) ; but 

 in the other the posterior wings and the tips of the anterior 



FIG. 65. Hemiptera. Bean Aphis (Aphis fabce) ; winged male and wingless female. 



wings alone are membranous. The inner portions of the an- 

 terior wings are hardened by chitine, and they are known as 

 "hemelytra" (Gr. hemi, half; and elutron, a sheath). Among 

 the more familiar examples of the Hemiptera are the numer- 

 ous species of Plant-lice (Aphides), the Field-bug (Penta- 

 toma), the Boat-fly, the Cochineal insects, and the Cicadas. 



The Cochineal insects are of considerable commercial im- 

 portance, as the dried and powdered bodies of the female con- 

 stitute the substance known as Cochineal, from which is ob- 



