THE PLANT LOUSE. 
43 s 
being broken open, difclole the numberlefs families that 
inhabit them f. 
Thefe galles or excrefcences formed by the plant loufe, 
and which often fo much disfigure the (hrubs upon which 
they grow, are in China, P trjia, 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 underflood. 
.The plant lice are feen to void from the anus a clear 
liquid fubflance, of a faccharine nature, which is greedily 
fought after by other infefts ; the fame kind of fug ar y 
liquid oozes from the extremities of two fmall horny ap- 
pendices that terminate the abdomen. It is i n purfuit of 
this fluid that the ants are feen to frequent thofe plants 
upon which the plant lice fettle in greateft plenty. From 
this ciicumflance, the former animals have been fuppofed 
hoftile to the latter ; while other naturalifls 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 effeftual method of preventing the depreda- 
tions of plant lice upon flowers and the leaves of plants, 
is fuggefled by thofe infeeds which live by preying upon 
them. The plant loufe-lion, or aphidivorous fly, either 
by inftinft or forefight, depofits her eggs in the midft of 
thefe animals ; and as foon as the larvae are produced, 
they devour hundreds around them, without the neceffity 
of any other movement than turning to the right fide or 
the left. This formidable infeft is furnilhetl with two 
tubercular 
f Reaumur ubi iupra. 
