25 



first pair of wings thickened, and the apical portion mem- 

 branous. The metamorphosis in this group is incomplete ; 

 the mouth parts are formed for piercing and sucking in both 

 the larval and adult stages. 



This order includes insects showing great diversity in 

 structure, especially with regard to wings, and in metamor- 

 phosis. In the case of many of the plant bugs (Fig. 17) 

 with the typical structure of fore-wings as mentioned above, 

 the second pair is membranous, and both sexes are winged. 

 In the case of the white flies, cicads, leaf-hoppers and 

 plant lice (Fig. 18) both sexes are winged, the wings 

 of both pairs are membranous throughout, while in the 

 scale insects (Fig. 19) the female is wingless and the male 

 is provided with only one pair of membranous wings. 



Fig. 19. Hemiptera. Scale insects, showing male and female scales, 

 and a winged male insect. 



All enlarged. (Imperial Dept. Agric.) 



