INSECT INTRUDERS. 



What is perhaps even more peculiar 

 than the food eaten is the fact that some 

 species are known to live for several years 

 in the soil feeding in this manner, the 

 period being the same for any given spe- 

 cies. For instance, the Americans have 

 what they term the ly-year cicada, the 

 mature insect appearingon thewingabove 

 ground only once during this interval. 



The grub moults its skin several times 

 in the soil and then just before the last 

 moult leaves the soil and crawls up the 

 nearest tree trunk (see p. 121) or tall 

 grass stem. The insect then sheds its 

 last skin, i.e., the last skin splits up at the 

 head end and the now mature winged 

 cicada, shown in the figure on page 120, 

 crawls out and soon commences its weird 

 song to attract a mate. 



You will doubtless have often seen 

 the last empty nymph skins on tree trunks 

 (p. 121) and have wondered what they 

 were, for they are to be found plentifully 

 on trees affected by cicadas. 

 122 



