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. 1 



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- 



FIG. 217. The Frog-hopper. ptera. The froth is given out by 

 Dorsal view ; B, lateral view, r, the little yellow arid green, or 

 brown ' six -!egged larvae who live 

 within it, and only leave it on 

 becoming winged adults. The full-grown insects have 

 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. 21 8. Scale Insects 

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

 the Mussel Scale of the apple tree (Fig. i^pis pomorum). 

 2 1 8). In some forms, the scale is replaced *> Scale coverin one 



, individual. 



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 



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

 T 1 75 of an inch across, on the larch stems. 



