NATURAL HISTORY. 
285 
Coccus .—This tribe of insects, of which the highly prized cochi¬ 
neal of commerce is the type, are found infesting plants in hot¬ 
houses, as well as several of our most useful fruit trees cultivated in 
the open air. The migratory white one, frequently seen on pine¬ 
apple plants, is highly injurious by withdrawing the juices, and dis¬ 
figuring the leaves, and still more when they fix themselves on the 
bottom of the stem among the roots. Both sexes are very minute 
when young; but the female after impregnation, grow to nearly a 
line in length, are then very sluggish, and probably die soon after 
they have produced their young. 
The next species is the well known brown scale, so frequently 
seen on orange, myrtle, and other plants, whose leaves are of a firm 
texture. In early life they are wanderers and invisible to the naked 
eye; but like the preceding, the females, after impregnation become 
stationary and large, by forming a shield over their bodies, under 
which they bring forth, and rear their numerous progeny. It has 
been questioned, whether the scale, from under which the young 
ones come forth, be or be not a part of the body of the mother. If 
raised from the leaf by the point of a knife, there appears to be six 
legs, or tentacula spread out, three on each side, of a whitish colour, 
partly attached to the shell, and also to the leaf; but may not this 
covering be formed of a exudation from their bodies, by which their 
young are protected ? 
Another, but much larger scale coccus is occasionally found in 
hot-houses, on peach-trees, and vines. This is, perhaps, what is 
called the vine-fretter. Their economy is like the last, only with 
this difference, that as their young increase in size, the lower edge 
of the shield is raised up, and the progeny are suspended in a white 
silky web as large as a middling pea, from which they issue forth 
when able to provide for themselves. 
Besides these cocci, common in gardens, two others are found in 
woods and hedges, one of which, coccus arborea, has lately found its 
way into gardens, seating itself on pear and apple trees, which it 
weakens considerably. In underwoods they attach themselves to the 
bark of red willow, and ash-poles, closely congregated together on 
the lower part of the stems. One of these has oval, the other kid¬ 
ney-shaped scales, or dorsal shields, about two-thirds of a line in 
length. Their injury to these forest trees, however, is imperceptible. 
But the most destructive coccus in this country is what is called 
the American blight, or mealy aphis. This is the great pest of our 
apple-orchards, and to the same kind of trees in nurseries. The 
young are so exceedingly minute, that they can, apparenly, enter the 
