CHAPTER XVIII. 



FERN-PESTS. 



VERY one who cultivates ferns, whether 

 in doors or out, in pots or in ferneries, 

 will, sooner or later, find that his pets are 

 liable to trouble from animal or vegetable pests, 

 and that some of these are only with great diffi- 

 culty to be exterminated. 



The common plant-lice {Aphis, PL 22, Fig. 9), 

 of which there are at least two species, collect on 

 the young fronds, and, owing to their gemmipa- 

 rous method of reproduction, increase with aston- 

 ishing rapidity. Dr. Packard, in his " Guide to 

 the Study of Insects, " states that it has been 

 shown, that, by this process, nine generations may 

 be produced, and in one case eleven generations 

 were obtained, in seven months. Ants, which do 

 no particular harm themselves, are very fond of 

 the sweetish secretions of the Aphides, sometimes 

 guarding them for future use. 



The Aphis may be destroyed by tobacco-smoke. 

 168 



