438 THE PLANT LOUSE. 



being bf oken open, difclofe the numberlefs families that 

 inhabit them f . 



Thefe galles or excrefcences formed hy the plant loufe, 

 and which often fo much disfigure the flirubs upon which 

 they grow, are in China, Perjia, and the Levant, applied 

 fuccefsfully in dying. Some fpecies formed in thefe 

 more northerly climes might probably be turned to the 

 fame ufeful purpofe, were their virtues underftood. 



The plant lice are feen to void from the anus a clear 

 liquid fubftance, of a faccharine nature, which is greedily 

 fought after by other infefls ; the fame kind of fugary 

 liquid oozes from the extremities of two fmall horny ap- 

 pendices that terminate the abdomen. It is in purfuit of 

 this fluid that the ants are feen to frequent thofe plants 

 upon which the plant lice fettle in greateft plenty. From: 

 this circumftance, the former animals have been fuppofed 

 hoilile to the latter ; while other naturalifts have deemed 

 it an indication of the friendfhip of the two genera for 

 each other : but it is neither from motives of love nor of 

 hatred that the ants repair in fuch numbers to thefe 

 haunts ; they feek to gratify their avidity, by devouring 

 their excrements. 



The mod effeiElual method of preventing the depreda-' 

 tions of plant lice upon flowers and the leaves of plants, 

 is fuggefled by thofe infe£ls which live by preying uporl 

 them. The plant loufe-lion, or aphidivorous fly, either 

 by infl.in6t or forefight, depoiits her eggs in the midft of 

 thefe animals ; and as foon as the larvae are produced, 

 they devour hundreds around them, without the neceflity 

 of any other movement than turning to the right fide or 

 the left. This formidable infect is furnifhed with twd 



tubercular 



f Reaumur ubi fupra. 



