286 
NATURAL HISTORY. 
pores of the epidermis, cause a swelling of the cuticle which soon af¬ 
ter bursts. The insects then may be seen in the openings, covered 
with a white efflorescence ejected from their bodies, intended it would 
seem, either for the purpose of concealment, or as a protection, in¬ 
stead of the scales with which their less destructive congeners are 
provided. 
As this species seems to prey on the juices which flow between 
the bark and wood, or on the tender substance of the envelope itself, 
the former years’ wood becomes denuded, and the lacerated edges of 
the wound become corky and monstrous, increasing in size till it en¬ 
circles the branch, when all communication with the roots is cut oflf; 
of course the branch, or if the insects have seized the stem, the whole 
head dies. Their manner of living and breeding is similar to that of 
the others mentioned above; the females attain the size of linseed 
nearly, and are constantly enveloped in the white covering peculiar 
to them, and by the buoyancy of which, it is said, they are wafted 
from tree to tree. They fix on the roots as w ell as on the branches 
of trees, and thus out of sight are often extensively injurious. The 
male is said to be a small black fly. The blood of these insects, if 
such it may be called, is always of a deep, lurid red, showing their 
affinity to the cochineal insect, indigenous to the Opuntia cochinili- 
fera, in South America. It has been stated, that this coccus is the 
sole cause of the disease called canker; but this is a mistake, because 
cankered trees, both those of the orchard and forest, are every where 
seen unaccompanied by this or any similar insect. It is very true, 
however, that the dismemberment and distortions of the bark caused 
bv either constitutional or accidental canker, are very likely to at¬ 
tract insects to nestle in, and this coccus as well as others; but the 
effects of constitutional canker may always be distinguished from 
those occasioned by the insect in question. It has also been said, 
that the American blight was introduced about 1788, from France, 
by the late Captain S. Swinton, R. N. who had a foreign nursery at 
that time, behind No. 6, Sloane-Street, Chelsea. But, however, 
true this mav be, there is no doubt the same insect was in England 
long before that period; as old crab-trees standing in woods and 
hedges in the middle counties were then, as now, covered with it. 
An insect of the same family is frequently seen on the underground 
stems of lettuce, endive, and dandelions. Of all these insects, the 
mealy one infesting pines, and the last described so pernicious in 
orchards, are the most destructive; they both prey on the vitals of 
the plant, and their introduction among such as are clean should be 
carefully guarded against. 
