114 
On the strength of these experiments Mr. Johnson recommends 
an emulsion one sixth of which is kerosene. Trees treated with an 
emulsion of this strength in the winter of 1904-05 were nearly free 
from scales the following July, and in January, 1906, only scatter- 
ing specimens could be found. In view, however, of the difference 
in climate and the absence of data as to parasitism, these results 
should not be regarded as conclusive for Illinois. 
Insect Enemies. 
It is to the insect enemies of the scale rather than to any human 
agency that the escape of our soft maple trees from complete de- 
struction has hitherto been due. Probably the most effective enemy 
Fig. 0. Coccoplnigus Iccanii, adult chalcid parasite of the cottony maple scale. 
Leng-th, less than ,'(; inch. (J. B. Smith.) 
is a minute black four-winged fly (Coccophagus lecanii, Fig. 6) 
which lays its eggs in the bodies of the young scales. The resulting 
larva lives as an internal parasite of the insect, develops to the adult, 
and emerges through a rounded hole cut in the back of the scale. Suc- 
cessive generations follow, and the scale population of a heavily in- 
fested tree may be almost completely destroyed in a single season 
by the parasite. Scales killed by it may be readily recognized by 
the hole in the back, and by their smaller size as compared with 
living individuals. Several other related species are known to infest 
this scale to a less degree. 
