292 



INTRODUCTION TO ZOOLOGY 



trees in drawing nourishment from them and causing distortion 

 of the branches, but also because it is thought that when pierc- 

 ing the tissues, the insect often 

 (\ • *^^ inoculates them with the spores of 



a Peziza, a fungus which causes the 

 disease known as Larch Canker.^ 



Family 2 : Cercopidae 

 (Frog-hoppers) 



The insects which cause the 

 accumulation of frothy substance 

 on many plants known as 

 " cuckoo-spit " or " frog-spit," are 

 the Frog-hoppers which form the 

 family Cercopidae of the Homo- 

 ptera. The froth is given out by 

 the little yellow and green, or 

 or beak pressed against ^^^^^j^^ six-legged larvae who live 



within it, and only leave it on 

 The full-grown insects have 



B- 



Fig. 217. — The Frog-hopper. 

 1, Dorsal view; JS, lateral view, c^ 



rostrum 

 the body. 



_ \ 



becoming winged adults. 



earned the name of Frog-hopper by the 



surprisingly big leaps they are able to 



make. 



Family 3 : Coccidae (the Scale Insects) 



Scale Insects are minute, degenerate 

 forms which live closely adhering to the 

 bark, fruit, or leaves of a tree, usually 

 hidden by a little scale — rather like one 

 valve of a minute mussel shell — formed 

 by an excretion from the body of the Fig. 218.— Scale Insects 

 insect which shelters below it, as e.g. in on Apple Tree {Myti- 

 the Mussel Scale of the apple tree (Fig. loj^pi^ P<y^^rri). 

 218). In some forms, the scale is replaced '> ^'^'^ covering one 

 by a powdery mass, when the creatures ™ ™ "''^' 



are known as "mealy-bugs." The full-grown insect is very 

 degenerate, but the larva is more active, and does much 



' This fungus, Dasyscypha calycina, causes little yellow discs, about 

 ^Jjj of an iuch across, ou the larch stems. 



