174 



Life-History of the Larch CJiermes 



The Progrediens larvae climb onto the Larch needles, and start to 

 suck, causing a bending of the leaf. 



After two moults at intervals of seven days (Fig. 8), these larvae 

 become divergent in structure in the third stage, one portion («) re- 

 maining elongate and slim (Fig. 9), and the other {h) becoming oval and 

 stout (Fig. 12). After a third moult, the former {a) become nymphs 

 (Fig. 10), and after a fourth and last, at the beginning of June, the 

 winged adult Sexiquirae (Fig. 11), which fly to Rpruce and produce the 

 Sexualis generation. The stout third-stage larvae {b) secrete a small 

 amount of wax-wool, then moult for the last (third) time, and become 

 wingless adult Progredientes (Fig. 13). These secrete much wax-wool 

 and lay 20-30 brownish eggs, which give rise again to Progrediens and 

 Sistens larvae: the latter hibernate in the first stage, the former, after 

 two or perhaps three moults, develop to adult Progredientes, but no 

 Sexufarae are produced from the first or any subsequent Progrediens 

 generation. Throughout the summer and autumn, the Progrediens 

 generations are continued until the time when the Larches lose their 

 foliage. 



Some of the Progrediens larvae produced from eggs laid by adult 

 Sistentes were kept under observation in Hertfordshire in March and 

 April, 1914, and developed as follows: 



6. 



The time from the hatching of the egg to the fiisf moult is therefore 



1 



